.308 Extrator

Manic Mike

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Greetings All,
I am experiencing an extraction issue on a .308, that I think I have narrowed down to the extractor. I am new to diagnosing problems (and building custom rifles), so forgive any ignorance on my part. The cartridge fails to eject from the breach. Everything works, cycles and feels fine, but more often than not, the cartridge is left in the barrel and the .308 tries to load another. After the bolt is removed, dropping a cleaning rod in from the muzzle, easily dislodges the stuck cartridge. This is a new Aero Precision rifle, 16" barrel with muzzle brake/compensator and an unbranded bolt carrier group. The BCG was a left over Mil-Spec unit from an upgrade; new, never used. I can post pictures as soon as the extractor is removed. The bolt was very tight in the carrier, so I installed a spare JP Rifles one piece gas ring. The bolt now moves freely and I am going to take a look at the extractor. Is there anything in particular that I should be looking for, that can identify the extractor as good or bad? If I had a bunch of $$$ I would simply buy a JP Rifles bolt and solve the problem.
Yours,
Manic Mike
 

RUTGERS95

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curious what brand of bcg

take apart the extractor and examine the spring and see if there is an o ring
 

Manic Mike

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The BCG is un-branded, but appears well made. It came from Moriarti Arms, who I do not recommend doing business with. They sent me a nice Bull Barreled .308, but forgot the BCG. After a lack of customer service, I bought a JP Rifles BCG and finished the rifle. After 6 months of going after them, through the credit card company, the BCG magically appeared in my mail box, instead of a refund. So, I built a Scout Rifle. When the bolt carrier was disassembled, I looked into the area that the bolt operates in; with intentions of polishing it a bit. But the machining was nice and a minor polish appears to have been done, so l left well enough alone. Changing out the JP Rifles single piece gas ring made a huge difference in the bolt operation; it is much smoother. I think I am going to add the single gas ring to all my AR platform Rifles.

Here are pictures and NO o-ring on the extractor spring!
bcg whole.jpeg

Complete BCG disassembled.
IMG_20220111_013512.SMALL.jpeg

Nicely machined and no need for polishing where the bolt rides.
IMG_20220111_013424.SMALL.jpeg

JP single piece gas ring; makes an incredible difference for $8.00; especially if you can not afford another JP Bolt Carrier Group
IMG_20220111_013327.SMALL.jpeg

The bolt and extractor.
IMG_20220111_013950.SMALL.jpeg

Close up of the extractor. I really want to polish this; do you polish BCG's? NO o-ring. Can I just put an o ring on it, or does it take a special o- ring?
IMG_20220111_013937.SMALL.jpeg

does there look like anything is wrong with the extractor? I am focusing on the cut out for the rim of the cartridge. It grabs and holds cartridge's and the ejector shoot them out when you let go of the cartridge. Any advice or comments would be appreciated.
Yours,
Manic Mike
 

RUTGERS95

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maybe replace the extractor spring and add the o ring then give it a whirl. If the extractor is not engaging, those two things are quick, easy, cheap to swap and test.

Not sure of the bcg brand but looks like recoil tech.
 

mtrmn

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    Looks like you had a dual spring in there, which I would think would render the O-ring unnecessary.
    What does your brass look like? did the extractor damage the rim of the case?
     
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    Ravenworks

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    Those springs are tore up,they look like they've been run over sand paper.
    Go to primary arms or Springco and get new inner and outer springs with the Oring.
    You should replace the ejector spring while it's apart.
    Did you test the bolt in the BCG to see if the one piece ring is working?
    Just because something says JP on it doesn't mean that it's good for your rifle
     

    Manic Mike

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    Good eyes! I did not even notice the double springs. BCG is back together and dummy rounds are not feeding well or releasing from the breech easily. I have contacted the barrel manufacturer. As to the Brass, the first few times the extractor did hold and the rim of the case was damaged during extraction; this should have pointed me towards the barrel, not the extractor. The feed issue involves the round angling up towards the breach and then jamming in place. It looks like the round is overshooting the hole in the barrel and hitting the top of the (God help me I do not know the particular nomenclature here!) Breech/Ramp. Here is a nice picture of the round jammed in the receiver. Bolt is on top, messing up my pretty dummy rounds and the round is angled up quite sharply. I changed magazines from a 20 round to a 10 round (Magpul) and the problem persists.
    Manic Mike
    IMG_20220111_180739.SMALL.jpeg
     

    Evintos

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    Extractor test - first one is to take the extractor pin, place it through the extractor that flick the extractor and see if it spins/rotates on the pin freely without binding. Measure extractor groove depth - ideally you're looking for something closer to 0.045" deep but if you can't measure the depth, take the extractor with your hand and claw the rim of a case on a table. You basically want to be able to drag brass across the table by the rim without having to put pressure onto the claw. This may not make sense to you. O-rings aren't necessary if there is enough extractor tension. Too much tension can actually cause other issues such as damaged case rims, failures to eject, etc. Generally speaking though if you can manually extract and eject a full mag of rounds, the extractor may not be the issue.

    Assuming the extractor checks out, the next thing I recommend checking is the headspace. Always a good idea when you're mixing/matching 308 components especially unbranded bolts and barrels.

    The next thing after that is I'd look at timing and gas issues. Failures to extract can be an issue of over gassing. Your BCG can cycle faster than norm essentially ripping the extractor off the case rim and other issues such as what appears to me like a bolt over base malfunction in your last picture. More description of this malfunction is - your bolt is riding on top of the round that is trying to feed into the chamber, rather than the lug being properly positioned behind the case head pushing the round from the rear. If this is your malfunction - bolt over base is usually a symptom of overgassing or sluggish feeding. Bolt is cycling forwards and backwards so rapidly that when the fired round does extract and eject, the bolt is already too far forward to properly feed the next round coming up the magazine. The other issue can be due to dirty magazine followers or weak magazine springs, the round isn't pushed up fast enough to position itself ahead of the BCG, this results in the BCG riding the cartridge and the friction between the bolt carrier/bolt lugs and cartridge body is what starts a partial feed. Bolt over base malfunctions however can also occur from being under gassed as well.

    Solution is to go with a heavier weight buffer or if you have an adjustable gas block, restrict the gas flow to correct the gas timing issue, clean the magazine follower and spring if you haven't done so or use new magazines. I suppose I should ask what buffer weight do you have in your build.
     
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    Manic Mike

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    The springs are new, as is the BCG. Replacing them should not pose an issue. The bolt would hardly move in the Carrier with the OEM 3 separate gas rings. I am not bashful about moving metal parts around and this set up was tight. I added a single piece gas ring, cleaned and lightly lubricated the assembly; it now moves smoothly and without excess play. I am not brand conscious, but JP parts have rarely been sub par. I will drop the manufacturer id and stick to the pertinent information moving forward. I do appreciate all the responses and advice!
    Manic Mike
     

    Manic Mike

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    Greetings Evintos,
    Thank you for the measurements on the extractor; this I can do. The extractor pin did not want to move until I pushed down on the extractor and suddenly it moved in and out without any excess pressure. The rifle is new and built with leftover components, with the exception of the following:

    Aero Precision enhanced upper receiver and hand guard
    Bear Creek Arsenal 16" .308 Parkerized barrel 1:10 twist Basic barrel, not precision match grade
    Strike Industries Japan Jcomp Type 89 Compensator

    The buffer is H1
    Standard gas block
    Carbine gas tube
    Magazines are Magpul new and clean
    Actually everything is maintained clean at all times; some kind of obsessive issue I have been told.

    I am in agreement that the round is not being moved properly. This is happening when fired and when cycled by hand. This is a fun rifle, so it will have to adjust with buffer weight and probably will not qualify for a gas block for a while. The common denominator is that the round is sticking in the chamber; fired or hand cycled/ factory ammo or dummy rounds (Starline brass). I really appreciate all the information and help from the members.
    Manic Mike
     

    Evintos

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    Greetings Evintos,
    Thank you for the measurements on the extractor; this I can do. The extractor pin did not want to move until I pushed down on the extractor and suddenly it moved in and out without any excess pressure. The rifle is new and built with leftover components, with the exception of the following:

    Aero Precision enhanced upper receiver and hand guard
    Bear Creek Arsenal 16" .308 Parkerized barrel 1:10 twist Basic barrel, not precision match grade
    Strike Industries Japan Jcomp Type 89 Compensator

    The buffer is H1
    Standard gas block
    Carbine gas tube

    Magazines are Magpul new and clean
    Actually everything is maintained clean at all times; some kind of obsessive issue I have been told.

    I am in agreement that the round is not being moved properly. This is happening when fired and when cycled by hand. This is a fun rifle, so it will have to adjust with buffer weight and probably will not qualify for a gas block for a while. The common denominator is that the round is sticking in the chamber; fired or hand cycled/ factory ammo or dummy rounds (Starline brass). I really appreciate all the information and help from the members.
    Manic Mike
    The bolded and red is what is leading me to say that you're really overgassed and you should be looking into an H3 buffer weight.
     
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    mtrmn

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    I agree an H3-weight buffer (5.4oz) is needed in a basic 308. What is the length of the buffer and what is the internal depth of the buffer tube?
    Your statement about not being able to move the extractor pin until you push it down is completely normal.
    On my PSA build, the gas tube was too short and I had to get an Armalite-length gas tube to make it right. It was 5/16" too short. The tube should terminate halfway in the cam pin cutout in the upper receiver. It can be a tiny bit longer, but not shorter than halfway of the cutout.
     
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    Quietguy88

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    That looks like a dwilson bcg. I have/had one. It went to the wastebin. All the machining was rough and the carrier was not properly reamed. Where the gas rings ride was very concave with absurd amount of chatter. It gave me countless issues. At the point I replaced all the parts... chasing issues.

    Your pictures look like a poorly nitrided piece. I would wager heavily that was one of the dwilson bcg's. A lot of people had issues with them.

    The bolt has a C inside the extractor pocket, same ejector and loose tolerances you are showing.

    You are most certainly over gassed. Look into an a5 receiver extension.

    I am running a superlative arms gasblock, a kynshot buffer(3.25" buffer at 5.5oz) sprinco red spring and forward control design 9position receiver extension.

    Granted, my rifle is 18" criterion hybrid contour m118lr barrel with a rifle length gas. Using an ultradyne apollo max muzzle brake it is very soft. Loud, but soft

    You will need at least a 5oz buffer. Maybe running the sprinco orange spring can help you tame that thing, if you are going to stick with the 2.5" long buffer and low weight.

    I advise using a 7.75" buffer tube(receiver extension). The a5 length or ar10/sr25 carbine length. So you may use generic ar15 carbine buffer length(3.25"). Using a milspec 7" extension will force you to use the shorter 2.5" buffer.
     

    GreenGO Juan

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    Being that its doing it hand cycled, Extractor and or case/chamber clearance issue???

    Ran into this issue when I replaced my bolt recently. The extractor that came with the new bolt did not work properly, and was jumping the case rim. Put the old extractor on, worked like butter, called the manufacturer, they replaced it. Do you have another extractor you can test on that bolt?

    Also what ammo are you using? You mentioned star-line brass which makes me think you are reloading(or at least making dummies) . How are you sizing the brass? Have you taken measurements on fired and unfired brass?

    With the bolt locked back, hand feed a round into the chamber with the barrel pointed down. Tilt the barrel up, will the round slide back out or does it stick and need to be mortared?
     

    rpoL98

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    Greetings Evintos,
    Thank you for the measurements on the extractor; this I can do. The extractor pin did not want to move until I pushed down on the extractor and suddenly it moved in and out without any excess pressure. The rifle is new and built with leftover components, with the exception of the following:

    Aero Precision enhanced upper receiver and hand guard
    Bear Creek Arsenal 16" .308 Parkerized barrel 1:10 twist Basic barrel, not precision match grade
    Strike Industries Japan Jcomp Type 89 Compensator

    The buffer is H1
    Standard gas block
    Carbine gas tube
    Magazines are Magpul new and clean
    Actually everything is maintained clean at all times; some kind of obsessive issue I have been told.

    I am in agreement that the round is not being moved properly. This is happening when fired and when cycled by hand. This is a fun rifle, so it will have to adjust with buffer weight and probably will not qualify for a gas block for a while. The common denominator is that the round is sticking in the chamber; fired or hand cycled/ factory ammo or dummy rounds (Starline brass). I really appreciate all the information and help from the members.
    Manic Mike
    it being a BCA barrel coupled with an economy-grade BCG, might be worthwhile to check headspace.
     

    mtrmn

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    The 2.5" buffer I settled on with my PSA build is a KAW Valley Precision 5.6oz used with a Sprinco orange spring.
    The OP needs to check the internal depth of his buffer tube and the length of the buffer itself to insure he doesn't have a mismatch.
     

    Manic Mike

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    This is lots of good information; let me digest it. H3 Weight is available to me; just pulled 3 tungsten weights out of a couple of 6.5 Creedmoor's that were over weighted. I will get pictures of the brass posted. Using reloads and factory loads. Brass examined by experienced re-loader and was deemed Possibly high in pressure to okay the first time and just fine after the second incident. Beginning to think over gassed and rough chamber. The first time a round got stuck, force was needed to remove it; this does not sound like the extractors fault. Waiting to hear form Bear Creek Arsenal, with their thoughts on the barrel. This was not an expensive barrel and if it needs a little polishing or if I need to finally buy a comparator and headspace gauge, so be it. Thank you for the input!
    Manic Mike
     

    Quietguy88

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    Usually the reason why an extractor will pop off the rim and leave in chamber is overgassed situation. That seems to be the most common issue in large frame builds. Now a bargain bin special barrel and bcg... you could have an unfinished chamber. By this I mean it was left rough. Shine some light down the muzzle and inspect. If it is stainless, it could be cleaned up pretty easily. Whereas, if it is chrome lined or nitrided... you basically boned.

    Headspace could be an issue.. but let us start with - using reloads how much are you bumping the shoulders back? I usually small base size and bump .002 to .003. Pending the brass, it may be a bit more than that.

    Your stack up of tolerances plus over gassed situation(most every build is overgassed, especially in large frames with shorter gas systems) may add difficulty in actually gauging "pressure" by looking at the brass. Stick to safe loads until you can use radar or chrony.

    Remember, if you try to extract the case too soon it will remain in the chamber. It has not contracted back enough to slide free.

    As far as the receiver extension lengths - if you have adequate travel so the bolt clears the bolt catch at rear most stroke, yet do not have any peening or visible strikes to the lower receiver or rear of gas key.. you probably are ok with the stackup of parts. However, this does not remove the need to actually measure your extension depth and buffer length. Hopefully you are following me here. Because again - stackup of machining tolerances. You could need to add a quarter or two into the buffer tube. Or, you may need to remove some of the rubber from buffer. Please note, this is all for example from issues I have seen before. It is not being given as an actual repair.

    You really need to try reducing the gas some how. A 5oz buffer on a carbine length gas system has a lot of gas. Most people run rifle length on 16" barrels with no issues.

    If you can run a pick inside the chamber and feel rough or uneven spots, you will need to address that issue. If it is relatively even and smooth.. no tooling chatter or rough edges that grab the pick, check headspace. If you close on a nogo 308 but cannot close on a field, it may be a 7.62nato chamber. Which.. pending on the stackups again could give some indication of pressure.

    In so far that everything is mechanically moving free with relatively good stackup in tolerances and the chamber is not the issue.. I would begin figuring a way to cut gas.
     

    Manic Mike

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    Okay, here is the first batch of information:
    Buffer is 4.8 oz; I can make that 5.4 oz. This rifle will have to do with buffer/spring changes, rather than an adjustable gas block
    Buffer length is 3.25". I also have 2.5" buffers available
    Buffer tube is 7" long; does this make my buffer too long?
    Buffer spring is 10.75" long Probably something that is 'mil-spec' or came from PSA. I have an 11.75" spring available
    Extractor springs are dual and new; they appear if they were sanded or ground flat. Since they are dual springs, I will remove the o ring I added
    I will get the extractor depth a little later, the micrometer is in the garage and it must be 55 degrees outside right now.
    The bolt moves smoothly within the carrier with the single gas ring. It was seriously tight with the 3 individual rings.
    The gas tube is terminating 1/4" short of half way down the cam pin cut out; ouch! I am getting about 23/64" of the gas tube inserted into the bolt
    Not sure what an A5 receiver extension is; would this be the 7.75" tube that is compatible with the 3.25" buffer I have installed
    Gosh this is so much fun!!!
    Ammo is both factory and reload
    Rounds drop in nicely and fall right out; don't think I have an issue here

    Dog says it is late and time to go to bed. I will sleep on this info...
    Manic Mike
     

    mtrmn

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    I fully agree with everything Quietguy and Evintos have posted.
    Okay, here is the first batch of information:
    Buffer is 4.8 oz; I can make that 5.4 oz. This rifle will have to do with buffer/spring changes, rather than an adjustable gas block
    Buffer length is 3.25". I also have 2.5" buffers available
    Buffer tube is 7" long; does this make my buffer too long?
    Buffer spring is 10.75" long Probably something that is 'mil-spec' or came from PSA. I have an 11.75" spring available
    Extractor springs are dual and new; they appear if they were sanded or ground flat. Since they are dual springs, I will remove the o ring I added
    I will get the extractor depth a little later, the micrometer is in the garage and it must be 55 degrees outside right now.
    The bolt moves smoothly within the carrier with the single gas ring. It was seriously tight with the 3 individual rings.
    The gas tube is terminating 1/4" short of half way down the cam pin cut out; ouch! I am getting about 23/64" of the gas tube inserted into the bolt
    Not sure what an A5 receiver extension is; would this be the 7.75" tube that is compatible with the 3.25" buffer I have installed

    Gosh this is so much fun!!!
    Ammo is both factory and reload
    Rounds drop in nicely and fall right out; don't think I have an issue here

    Dog says it is late and time to go to bed. I will sleep on this info...
    Manic Mike

    -You need a 2.5" buffer with a 7" deep tube. That buffer will need to be ~5.5oz and there's only room for 2 weights, so the buffer body will have to be made of something other than aluminum. Mine is a KAW 5.6 oz using a Sprinco "Orange" spring

    Easiest way to make 100% sure you start with the right recoil system is install the Armalite buffer kit which includes the tube, buffer and spring. I can get you a part number shortly. This and the "A5" extension are the same 7.75" depth and are compatible with 3.25" buffers.
    ETA- https://dsgarms.com/rifle-accessories-arm10702302
    Out of stock, but there's your part number for an internet search. You could also go with these other part numbers.


    You also need the Armalite - length "carbine" gas tube. Part numbers upcoming.
    ETA- https://dsgarms.com/upper-receiver-parts-arm10007005

    The AR308 was never standardized by the military like the AR15 was. Every company came up with their own measurements and changed them at will. Mix/match large frame ARs are a nightmare to make run properly.
     
    Last edited:

    Quietguy88

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    The A5 buffer tube length will measure 7.75" and you need the 7.75" tube for using a 3.25" buffer. That is why KAC and Armalite use the longer tube. So large frame rifle can use ar15 h3 buffer.

    If you have a 7.00" tube depth, it requires a shorter 2.50" buffer.

    So, if you are running the 3.25" buffer in a 7.00" buffer tube, you will be short stroking roughly 3/4".

    You also need a longer gas tube if I am understanding this. The gas tube should terminate at approximately center of cam pin pocket. It can be slightly longer or shorter.. however, longer is better. In so far the gas tube does not bottom out inside the gas key. Sometimes it will be enough to prevent fully locking the bolt in battery. Other times, the tube will flex a little and you may not notice while firing. It would be diagnosed by feel when installing bcg to upper.

    As far as springs - use either a red or orange sprinco spring. The 3/4" difference between a 7.00 or 7.75" receiver extension is not going to make any real difference. In so far your parts are all stacked up.
     
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    Quietguy88

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    Not to derail, but here is mine. 400m on 8". GGG m80. T536 steiner battle optic. Prone unsupported, kneeling unsupported and standing supported.

    Just some block leave fun.

    I know very little, only what I have experienced.. hope can help you a little.

    Sharing, so you do not think I am that chair commando.

    Got a bunch of clearanced stuff, hence the mix match colors. She ugly, but she shoots.

    Ohyea - ultradyne apollo max is a nice comp. Knocks anything off the bench, ground, or other shooting support but.. damn. This setup runs softer than m4 throwing m855a1
     

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    Manic Mike

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    Thank you all for your time and information (especially links/part #'s). Please bear with me as I evolve from 'Spray and Pray' to precision long distance rifles, gunsmithing and reloading. That is a lot to learn in under a year. As I am working towards the root of this issue, I just recalled a crucial piece of information. Fist time out with the AR, it jammed and had a funny rattling sound. On inspection, the buffer had come apart in the buffer tube. I found all the parts, except the roll pin that should hold on the plastic buffer. So there is a 50/50 chance I was negligent and did not put the roll pin in (I am Detail Oriented, but not perfect). I may have to sneak a few $$ out for the buffer and gas tube mtrmn was kind enough to post links for; your time is not wasted, I learn quickly and do not ignore wisdom placed before me.

    Can I cheat on the head space, by checking a round in my Wilson head space gauge, then fitting the round into the chamber? If not, what is my best long term solution for checking head space and other necessary measurements/specifications? I am learning reloading fast and need to deal with quite a few calibers. Comparators and such are on the purchasing list, but I spent all my Stimulus Checks (and most of my spare $$) on way to many Nice rifles, Nice pistols and automated reloading equipment. I was smart enough to do this right before I quit being a Biochemist and the Wonderful salary that came with the job.
     
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    Evintos

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    Can I cheat on the head space, by checking a round in my Wilson head space gauge, then fitting the round into the chamber? If not, what is my best long term solution for checking head space and other necessary measurements/specifications? I am learning reloading fast and need to deal with quite a few calibers. Comparators and such are on the purchasing list, but I spent all my Stimulus Checks (and most of my spare $$) on way to many Nice rifles, Nice pistols and automated reloading equipment. I was smart enough to do this right before I quit being a Biochemist and the Wonderful salary that came with the job.
    Best long term solution is buying a Go Gauge and Field Gauge for each caliber however these gauges aren't used often so from a price/utility perspective, it may be cheaper simply to take the firearm to a gunsmith and have them check headspace for a small fee. If you ever plan on assembling more firearms (or replacing parts from wear and tear and use) with the same caliber (lets say you're doing another 308 AR build + a 308 bolt action build or a 308 barrel/bolt swap), then it'll be worth picking up gauges. My recommendation is the "Down & Dirty" set from https://mansonreamers.com/ for 308.

    1642100906008.png


    The Wilson Case gauge (and general case comparators) are more for measuring already fired cartridges in order to determine sizing die set up for shoulder set back. Since headspacing should be done before the first round ever gets fired, one can make the argument that if you've already fired a round out and nothing blew up, it should be safe so what's the point of measuring headspace. Counter argument is that you might be right on that borderline of safety despite being functional and that any small dimensional change whether from debris, brass size, powder variation, temperature, etc. will nudge you into catastrophic failure territory. What is your tolerance for risk? I would throw this out there as well. For a factory built rifle, the responsibility for repair/replacement of faulty firearms usually lie with the manufacturer. If the ammunition is at fault, it's the ammo manufacturer's responsibility. For home builts/assembled, the responsibility lays with you. Do you want to shoulder the cost of replacing receivers, barrels, bolts, etc. that blew up due to improper headspace?

    As for the potential buffer damage, it is very possible that it was damaged from slamming excessively hard to the rear of the receiver and damaged the bumper portion.
     

    Quietguy88

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    For the cost of reasonable gauges... It would be worthwhile investment. Like any tool - it can and likely will be useful later. Either another rifle for yourself or a friend.

    A cheap buffer can get ate up with overly gassed action. It is not unheard of.

    Get the proper gas tube and an adjustable gas block. Either vent excess gas forward or restrict gas going back. I like superlative arms gas blocks. Do not get hung up on name brands or differences. Just get a quality unit, use it.

    Get a quality receiver extension with internal depth of 7.75", get the red and orange sprinco spring, pick up a quality h3 ar15 buffer.

    Adjust the gas so ejection is at 0330, 0400 from ejection port.

    Sight the weapon and use it. Replace parts as they are shot out.
     

    mtrmn

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    Thank you all for your time and information (especially links/part #'s). Please bear with me as I evolve from 'Spray and Pray' to precision long distance rifles, gunsmithing and reloading. That is a lot to learn in under a year. As I am working towards the root of this issue, I just recalled a crucial piece of information. Fist time out with the AR, it jammed and had a funny rattling sound. On inspection, the buffer had come apart in the buffer tube. I found all the parts, except the roll pin that should hold on the plastic buffer. So there is a 50/50 chance I was negligent and did not put the roll pin in (I am Detail Oriented, but not perfect). I may have to sneak a few $$ out for the buffer and gas tube mtrmn was kind enough to post links for; your time is not wasted, I learn quickly and do not ignore wisdom placed before me.

    Can I cheat on the head space, by checking a round in my Wilson head space gauge, then fitting the round into the chamber? If not, what is my best long term solution for checking head space and other necessary measurements/specifications? I am learning reloading fast and need to deal with quite a few calibers. Comparators and such are on the purchasing list, but I spent all my Stimulus Checks (and most of my spare $$) on way to many Nice rifles, Nice pistols and automated reloading equipment. I was smart enough to do this right before I quit being a Biochemist and the Wonderful salary that came with the job.
    Just to clarify, the KAW buffer kit I linked will be a std 7" deep AR15-length tube (which you already have) and a 2.5" buffer (required to work with the AR15 tube in a 308) with a properly sized spring with the right amount of spring pressure for the 308. The proper spring is just as important as the buffer.

    I had my PSA 308 tore down for cleaning and when going back together, I mistakenly picked up a std AR15 buffer spring instead of the 308 spring. It seemed to work fine for a while, but the gun would not lock back on an empty mag and occasionally tried to lock back by catching the CARRIER rather than the BOLT. After much headache, I finally figured out what I had done and pulled the spring out. Sure enough there was no orange paint on my supposedly orange spring. Then I went on a search of all my AR15's until I found one with an orange spring. Apparently the AR15 spring was coil binding and was longer when compressed, keeping the BCG from moving far enough rearward.

    Don't forget, even after you get the recoil system sorted out, there's still a questionable quality BCG involved. So if you still have some problems you may start looking at that.

    If you go to https://sprinco.com/ar-buffer.html you'll see a couple of links to PDFs. They are very educational.
    You can also go to https://heavybuffers.com/ for more education and top of the line products and service.
     
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    RUTGERS95

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    man you guys make this all sound so fking complicated
    buy a good bcg
    standard carbine buffer tube
    308 heavy carbine buffer (KAK has them for $30) and 308 carbine spring
    no issues in multiple builds

    this is not rocket science
     
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    rpoL98

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    Manic Mike

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    I checked around and the 8" buffer tubes are available, but pricey. Combined with a spring and shipping form multiple vendors, the cost is within $45.00 of a JP Silent Captured Spring. I have plenty of weights and different springs for the SCS system and am seriously considering it. For $45.00 more I could have a fully adjustable buffer system, with different weights and multiple springs; any opinions on this? I checked the chamber visually and with a pick; everything is smooth. Dummy rounds drop right in and fall right out, with a slight bump. I am hoping the issue is over gassing and timing. The correct length gas tube is on it's way. The ammunition specialist also mentioned the possibility that the timing was off and the bolt may be attempting to remove the cartridge before it has had a chance to recover from the expansion of firing.

    IMG_20220113_172434.SMALL.jpeg


    The dual springs on the extractor are brand new and ground flat on the ends. I removed the o ring that was added and reassembled the BCG.

    IMG_20220113_171427.SMALL.jpeg


    The groove in the extractor is about .039" deep. It really looks ugly when magnified. Can this be polished if I don't mess up the straight side?

    IMG_20220113_171626.MEDIUM.jpeg


    Same extractor, different view. It was harder to measure the depth of the groove than I first thought; best approximation is .039" deep. The extractor does grab and hold/move a cartridge.

    IMG_20220113_171605.SMALL.jpeg




    Bolt with single piece gas ring and firing pin. There is a little odd wear at the rear of the extractor.
    IMG_20220113_172028.SMALL.jpeg

    The inside of the upper is clean and not showing any signs of abnormal wear. The bolt engages and disengages smoothly. I believe the fibers are cotton from a swab used to clean up the area.
    IMG_20220113_172639.SMALL.jpeg

    Thanks again for the information and advice. This is a fun little .308 and I look forward to tuning it to work perfectly.
    Manic Mike
     

    Manic Mike

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    I am currently using the KAK adjustable Buffer system and contacted them today. They did not have a buffer tube that fit the 3.25" buffer. KAK also has dual ejector BCG's and all my other AR platform rifles have adjustable gas blocks, but this is a low budget, left over build. I have quite a few new expensive rifles that I will probably need help tuning also. Those are why this one will be lucky to get a SCS spring system, if I can sneak out the $$!
     

    Quietguy88

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    Honestly... I have used the SCS JP system. Comparing an slr gasblock with jp scs rifle to my rifle using a kynshot buffer, sprinco red spring and superlative arms gasblock... I will never run the SCS. I think it is very expensive and gives no advantages. Between red and orange springs, you have two very well confirmed spring rates with large amounts of proven success. You need an h3 buffer minimum. So, just run the ~5.5oz buffer, have two cheapo springs and wallah.

    I have no experience with the bcm a5 receiver extension, but it is fairly low priced. Again, I opted to use Forward Control Design's(FCD) 9 position receiver extension.

    From memory, it is the #5005 kynshot buffer. These guys claim to make hydraulics for heavy use applications in military. Who knows if true.. I do know the 249, 240 and various other weapons will see crazy abuse by typical joe snuffy, shitbag privateer and laugh it off. Can it fail? Yeah. But, in worst case - I can still source any h3 ar15 buffer. Something with a stainless body and three tungsten weights will be all you need.

    You can very easily buy everything for under $150. Receiver extension, two springs and a buffer. You already have a collapsing stock.

    I have no experience with KAK brand.

    Will say this. A 5.5oz buffer and full mass bcg is a minimum. These big frames just seem to run better when adding more weight to the system. Again, having a low mass carrier and jp scs... that rifle has more recoil, muzzle hop and is less pleasurable to shoot. They are using same part number criterion barrel. Same chamber, same handloads. The difference is bcg and buffer/spring.

    I will not say JP has bad products. Though I will say you pay 30%more for their products.

    Far as scs goes - i will not be buying them anymore. There can be too much of a good thing. Tinkering for hours between which spring or how many tungsten...

    I already learned what armalite and kac established by experience... the same way.. you need a minimum of one pound in bcg with an five ounces in buffer to make the guns run. Anything less makes problems. Add in most manufacturers over size their gas port and suddenly you have the issues which are described here.

    Barrel manufacturers would rather over gas and rattle a rifle into loose junk than undergas and make a potential choke machine. Because the rattled loose rifle still "runs".

    Your gas tube is too short. Far too short. Replace it.

    That bcg was known to be junk. Sadly, I paid for the "quality model" when I got mine. I swear they sent me a reject. Multiple people played the swap extractors game along side change gas rings and pray. Most of them went through multiple parts and ended up gassing the rifle heavily to make it mask issues. Your miles will vary. As you can tell - I have no nice things to say about the lack of workmanship that was used when cobbling parts out of metal.

    Look man, large frame gas guns are not cheap. I learned the hard way - budget prices are usually going to bring risks.. they may be TDP m4/m16 'in spec' but that does not mean squat for non standardized pieces.

    As example - pending on in spec tolerances of each part, you may need to address offset buffer retainer bores. Or adding a shim/stack washer behind the buffer. It is very common.

    Buy some known reputable parts. Pay it up front and use the saved money for rounds. I learned the hard way. By doing what you are doing. It resulted in a pile of junk parts eating space in a drawer. That are good for nothing. I spent three times the money playing that way. I should have bought what I have now and spent the "saved money" on more rounds. Would have made me so much more happy. Three times the amount of boomboom trigger time, less wasted space in my toolbox... less headaches.

    You spend your money, you take them chances.

    Solid advice has been given by others with far more experience than I have.

    The chamber looks plenty fine from the assumption I can make based from glancing at photo. You just need to swap gas system and action(recoil) system pieces.

    I like ar15discount website. Your mileage may vary. They give me a nice discount. They carry most the brands I like.

    Using $4 castle nuts and end plates is not a bad idea. Using $30 receiver extensions and buffers... may not be as smart.

    Plugging the ar15discount - they often have flash sales. I scored some nice top shelf parts for twenty to thirty percent off during the holidays. Just know what you are looking for and do not impulse buy. Research before hitting ship it button.
     

    mtrmn

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    Quiet guy is talking good sense. KISS. Run with the prescribed buffer weight and the right spring and proper buffer length. That too-long buffer you had would make any AR choke by itself. Nevermind the atrociously-short gas tube. You can see in your pic how far the tube enters the gas key--just barely. Get these 2 items fixed before you start throwing more money and time at it.
    Oh, and on that KAW buffer kit I linked, if you indeed have a 7" deep tube you don't HAVE to change that tube out. Just stick the new spring and buffer in the tube you already have.
     

    Quietguy88

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    Here. Buy the red and orange spring both. Start with red. This allows you to swap into a more stiff spring(orange) if you cannot get ejection proper with red spring and gasblock tuning. If your gas block journal on barrel is 0.750" then get this gasblock. If memory serves, it came with a gas tube roll pin. I use this one and it works well. Read their instructions and use bleedoff method. It really helps keep the rifle clean. I ran over 300 rounds of m80. It was some pretty hot loaded ammo. 44.5grains of ball powder behind 147gr fmjbt's. It looked less dirty than my m4 after a zero and qual session.

    As a note - be sure to measure the spacing of gas journal shoulder on your barrel and actually set the gasblock to sit with it's port centered over the barrel's port. I measure from the edge of barrel gas journal to edge of port in barrel. Then compare that to the gasblock edge to edge of gasblock port. You would be amazed how many variations will be found here. This is the root of many problems for builds.

    Get the proper length gas tube and a set of washers. Pre-stressing the muzzle with crush washers will really change point of impact. I honestly like jam nut muzzle devices. However - for a do it cheap and make it run... a set of washers, new buffer and springs, adjustable gasblock and new gastube will set you right.

    In so far you measured properly the buffer tube internal depth, the buffer length and have a solid knowledge of your barrel dimensions.. these parts will get you running reliably. Enough to reduce gas, get it shooting consistent and enjoy taking the rifle out.

    *edit*

    The gasblock is currently on flash sale for 20% off. Reason why I recommend it.. quality piece, it works very well and the price is right.
     

    RUTGERS95

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    no disrespect to anyone here but I feel like I'm in a German engineering design room and we're trying to complicate the spoke and wheel for a new car lol This is easy and it's not like 10yrs ago where there was so much more variation in parts. bolt not catching, check extractor set up. since your extractor is out, run a case along it and see if it catches (you said you don't have tool to measure the depth) If it catches, its fine. You did swap the spring etc. now function check

    I've used all below in the last 4 builds except the aero gas block as it's new and prior I used the slr however, it's in a current build and running great at almost 2k rounds. 2 clicks left to start first shot to check bolt hold then more 2 clicks left to run all ammo including underpowered pmc and wolf which it does.

    gas system set up and the bcg are most important parts of the rifle for building 308s. here you go; (you could get all of this from Aero but it will cost more and you'd still need to get the heavy carbine buffer elsewhere). You could always replace the bolt set up if you still have issues, carrier I'm sure is fine.

    308 heavy carbine buffer (I'm on my 5th one with zero issues)
    308 carbine spring (don't use the orange, it's too heavy and causes stovepipes unless you open your gas block all the way which is defeats the purpose of the adj gas block. no need for a heavy spring, all you need is the standard 308 carbine spring)
    standard carbine buffer tube
    aero precision adj gas block

    here is my most recent build (fun gun with spare parts that turned into a build) with all the parts listed above. This now has close to 2k rounds without a single hiccup. I used a cheap KAK value line barrel as I've used them before with a lot of success and they are surprisingly accurate for value barrel. Dare I say, I get the same accuracy with them as with my BA barrels. Obviously not on par with lmt ss barrel but with surplus dag, she is printing right at moa. I only shoot surplus and steelcase in this and I've cleaned it 2x (first time was after initial break in and function check to inspect everything after 500 rounds. 2nd was at about 2k). A 1-8x now sits on it
     

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    Quietguy88

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    no disrespect to anyone here but I feel like I'm in a German engineering design room and we're trying to complicate the spoke and wheel for a new car lol This is easy and it's not like 10yrs ago where there was so much more variation in parts. bolt not catching, check extractor set up. since your extractor is out, run a case along it and see if it catches (you said you don't have tool to measure the depth) If it catches, its fine. You did swap the spring etc. now function check

    I've used all below in the last 4 builds except the aero gas block as it's new and prior I used the slr however, it's in a current build and running great at almost 2k rounds. 2 clicks left to start first shot to check bolt hold then more 2 clicks left to run all ammo including underpowered pmc and wolf which it does.

    gas system set up and the bcg are most important parts of the rifle for building 308s. here you go; (you could get all of this from Aero but it will cost more and you'd still need to get the heavy carbine buffer elsewhere). You could always replace the bolt set up if you still have issues, carrier I'm sure is fine.

    308 heavy carbine buffer (I'm on my 5th one with zero issues)
    308 carbine spring (don't use the orange, it's too heavy and causes stovepipes unless you open your gas block all the way which is defeats the purpose of the adj gas block. no need for a heavy spring, all you need is the standard 308 carbine spring)
    standard carbine buffer tube
    aero precision adj gas block

    here is my most recent build (fun gun with spare parts that turned into a build) with all the parts listed above. This now has close to 2k rounds without a single hiccup. I used a cheap KAK value line barrel as I've used them before with a lot of success and they are surprisingly accurate for value barrel. Dare I say, I get the same accuracy with them as with my BA barrels. Obviously not on par with lmt ss barrel but with surplus dag, she is printing right at moa. I only shoot surplus and steelcase in this and I've cleaned it 2x (first time was after initial break in and function check to inspect everything after 500 rounds. 2nd was at about 2k). A 1-8x now sits on it
    Would not go so far as to say I am attempting an engineering class. However, will say I have been on the badluck run enough to know a few things.

    The extractor will bottom out against the case's groove. The rim of case will not contact the relief cut on extractor. When all things are proper.

    I have never ran KAK. They been around for a few years and are expanding their facilities. I actually grew up within a short drive of their location. I fully support local businesses as well..

    Nothing wrong with using the 7" buffer tube or any of the short buffers either.

    You nailed it; use parts that are known good and have proven success. Agreed entirely. There are plenty of options out there.

    Only going to offer input based upon my person hands on experiences. Positive or negative, however it was.

    Sometimes that orange spring is needed. For whatever reason.

    The parts market has gotten largely better. Undoubtedly. More importantly though, is the information of what specifications to build compatible combinations.

    You would be surprised with how little I invested in many things on my marksman rifle. On the other hand, I wasted a lot of money in some things that never worked.

    I never tried DAG. However the GGG m80 runs moa out of mine. Hate saying it because... someone gonna buy it up and make me pay more.

    *correction*.. the GGG m80 rounds are 4moa and have constant issues. Send any you have my way for proper disposal.

    You know - I had a fellow ask for help with installing a traditional crosspin trigger. They had no clue. I absolutely hate those drop in cartridge assemblies.. also had another guy not understand the gasblock is not simply shoved against the barrel shoulder and forgotten about.

    Would rather share guidance based upon observing other's struggles. So to prevent further struggles for the other party.

    *shrug*

    Some gucci parts are nice and I can feel a difference. Others.. are not so nice. Nowdays - I know what is worth the extra money.
     

    RUTGERS95

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    Would not go so far as to say I am attempting an engineering class. However, will say I have been on the badluck run enough to know a few things.

    The extractor will bottom out against the case's groove. The rim of case will not contact the relief cut on extractor. When all things are proper.

    I have never ran KAK. They been around for a few years and are expanding their facilities. I actually grew up within a short drive of their location. I fully support local businesses as well..

    Nothing wrong with using the 7" buffer tube or any of the short buffers either.

    You nailed it; use parts that are known good and have proven success. Agreed entirely. There are plenty of options out there.

    Only going to offer input based upon my person hands on experiences. Positive or negative, however it was.

    Sometimes that orange spring is needed. For whatever reason.

    The parts market has gotten largely better. Undoubtedly. More importantly though, is the information of what specifications to build compatible combinations.

    You would be surprised with how little I invested in many things on my marksman rifle. On the other hand, I wasted a lot of money in some things that never worked.

    I never tried DAG. However the GGG m80 runs moa out of mine. Hate saying it because... someone gonna buy it up and make me pay more.

    *correction*.. the GGG m80 rounds are 4moa and have constant issues. Send any you have my way for proper disposal.

    You know - I had a fellow ask for help with installing a traditional crosspin trigger. They had no clue. I absolutely hate those drop in cartridge assemblies.. also had another guy not understand the gasblock is not simply shoved against the barrel shoulder and forgotten about.

    Would rather share guidance based upon observing other's struggles. So to prevent further struggles for the other party.

    *shrug*

    Some gucci parts are nice and I can feel a difference. Others.. are not so nice. Nowdays - I know what is worth the extra money.
    all good brother, you know message boards don't show tone so posted only in the nicest of way and smiling though sometimes doesn't come across that way. You make some great points it's just I think for the OP, he just wants to get is rig running so keep it simple kind of approach. I will say this and don't think I saw it earlier but I wonder if his gasblock is seated correctly given the depth of the gas tube?

    GGG is great, big fan. I have quite a bit of DAG and let me tell you, if you can get some do it because it's the best milsurp you can get. I find it reliable and more accurate than modern production 'match' ammo like ppi (old green box was the cats meow) and the like, FGMM and Hornady excluded of course. I also have done well with zqi but people hate it. I look at it like this with ammo, if I want match then you buy fgmm and all else is just fodder so I don't get too upset over too much with it but DAG is fantastic.

    orange spring-everytime I used one it created issues for me. I'm not sure why it unless you have an adj gas block and it's opened, I always got feeding issues. Now the one I have sits in the bottom of my bin. Hell I'd gladly send it to OP free of charge as that's the kind of guy I am and have been fortunate with firearms community; pay it forward!

    so uhhhhh, where you getting your GGG and how much hahahaha
     
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    rpoL98

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    it's interesting that BCA elected to use the Armalite AR-10 gas tube lengths. That's kind of unusual.

    separately, I've had good luck using the $15 HeavyBuffers 308 carbine spring. I have no idea if there's any kind of magic sauce or pixie dust involved. I have it in about a half dozen AR-308 lowers. I've also used the HeavyBuffer 308 carbine buffer, and the Expo and KAK 5.3oz 2.5" buffers. FWIW.
     
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    Quietguy88

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    The GGG is gone damnit. Gone right down the shooting lane.

    I used about 500 rounds of zqi. I had zero issues. It was not bad. GGG out grouped the zqi though.

    That said - my rifle seems to shoot almost any same batch m80 at 1 to 1.5moa when inside 500m.

    Agree - the OP seems to be after the lowest cost fix. Hell. An orange spring and the 5.5oz buffer may just fix his issue enough to make it run. $75 shipped to his door. Out and running. No gas block, no nothing. He is mechanically short stroking due to using a 3.25" buffer in a 7.00" tube. With full gas, even using the wrong gas tube may not be an issue.

    That stated, I fully suggest changing at very least his gas tube and verifying the gas block port is "centered"(close as can honestly be) over barrel gas port.

    All in - I am expecting he has something to share in about two, three weeks tops.
     
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    Quietguy88

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    Oh, I had a 10oz rifle buffer from slash. Still do. It ran pretty well, the armalite rifle spring, slash 10oz buffer and full gas.

    However.. the sup arms gasblock, kynshot 5.5oz buffer and sprinco red spring combo... between having the gucci 9position a5 buffer tube adjustability, the better cheekweld of bcm's stock and well.. the kynshot buffer - I was concerned to be an expensive gimmick. It has like no resistance to hand compression. Somehow the stackup of parts - man.. that 10oz buffer just did not compare.

    On 5x I watch my rounds slap 8" steel at 100. While kneeling and standing offhand shots.

    Is what is.

    Slash treated me great. I had zero issues with his products. He had amazing turn around time and sent countless emails with me. All I can say.

    Though - for my next m16-esq spr build... gonna use the same gucci 9position tube, buttstock and a 7oz kynshot buffer with sprinco green. Setup on rifle gas with suppressor and suparms dump to atmosphere. Simply based upon my most recent experience.
     

    Steve_In_29

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    Manic Mike

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    Waiting on a call back from AR15 Discount. Buy once, Cry once is a good life practice! While this is a fun gun, all the parts I bought were top notch, the leftovers were leftovers for a reason. I am not an ASK HOLE and have taken the communities advice on good parts. Should have an update in a few weeks, as noted. Thank you all again for help on a Fun Gun; I would rather solicit advice from intelligent people, than get it from what is generally available elsewhere. (I am not as Politically Correct as that last sentence, I just did not want to offend the other forums.)
    Yours,
    Manic Mike
     
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