HELP! Aero M5 not running

kingofthepoors

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This is my first 308 build and its been nothing but headaches. I have the JP gas block adjusted almost all the way out. I have about ten rounds through it and have only gotten it to eject twice. It has yet to pick up another round. Im thinking my spring is too strong or something is up with the buffer. Im trying to figure out the specs need for an M5 build but not having much success. Any questions or pictures needed Ill try to get to ASAP. Id like to get this thing running.
Parts used for gas/recoil-
Luth AR 308 buffer, spring and tube
Aero Stainless rifle gas tube
JP adjustable gas block
IMG_3148.jpg
tube end.jpg
tube length.jpgbuffer spring.jpg buffer length.jpg
spring length.jpg
LUTH AR Buffer.jpg
gas block.jpg
list.jpg
 

kingofthepoors

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Get a heavier buffer weight. H2 always.
Are H2 buffers the shorter ones for carbine tubes/springs? Will that work for a rifle buffer tube?
I dont have a scale but the websites specs list my buffer weights at 5.3oz and 11.2oz for the unit.
buffer specs.jpg
 

bfoosh006

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This is my first 308 build and its been nothing but headaches. I have the JP gas block adjusted almost all the way out. I have about ten rounds through it and have only gotten it to eject twice. It has yet to pick up another round. Im thinking my spring is too strong or something is up with the buffer. Im trying to figure out the specs need for an M5 build but not having much success. Any questions or pictures needed Ill try to get to ASAP. Id like to get this thing running.
Parts used for gas/recoil-
Luth AR 308 buffer, spring and tube
Aero Stainless rifle gas tube
JP adjustable gas block
View attachment 7356057
View attachment 7356040
View attachment 7356039View attachment 7356036 View attachment 7356035
View attachment 7356038
View attachment 7356046
View attachment 7356042
View attachment 7356060




Your profile pic sure looks familiar. Lol... and FWIW... not all forums are the same.

First things first, will it lock back on a single, mag fed and fired round ? Repeatably and consistently ?

Will the BCG lock back manually ( via the charging handle ) with a empty inserted mag ?

Have you tried any other mags ? Lancers have VERY stiff springs, and can cause drag on some BCG's.

FWIW... your parts "should" be working together... so it might be a Gas Block alignment issue, or just needs some break in... or the mag spring thing.

Let us know... IMHO, anything Large Frame AR...can be fixed , fairly easily.
 
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kingofthepoors

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The picture may look familiar. I did it for tribute. I spent a day with the gorillas and it didnt turn out well for me. This place seems much better.

I was running the bcg dry, I had heard from a few places it likes to be ran wet so I sprayed the hell out of it last range trip. The gas block I actually moved. We had it directly against the journal and I saw in a few threads that can be a problem. I contacted Ballistic Advantage and they responded with this. So moved it roughly two credit cards with off.

*edit*
I forgot to answer your questions. I have tried a 20 round lancer and 10 round magpul. I have pretty much all variations so Ill bring a few next time. Ive mainly been taking the 10 round magpul to zero it. The bolt can lock to the back manually but has yet to as it hasnt picked up a round yet. The closest Ive gotten to it cycling was it ejected and pushed failed to put in a new round. It moved said round like halfway out the mag though. That was with my gas almost all the way opened up. That seemed like something was wrong so I just stopped for the day. I havent tried just one round and seeing if itll lock back, I usually run 2-3 rounds in the mag. Ill try that the next time I go out.

BA's response to my question about gas block placement on BA Modern Series 20"
BA port answer.jpg
 
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kl3309

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Too damn close to D.C.
Two credit cards' thickness is way more than 0.025". Did you ever shoot it with the gas block back against the shoulder? Did it work?
 
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celltech

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When charging is the action smooth...does the BCG easily come off the gas tube and seat all the way back in, lugs have rotated, etc.. Neighbor's AR10 was cycling for crap and it was an oversized gas tube causing the BCG to bind.
 
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kingofthepoors

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Two credit cards' thickness is way more than 0.025". Did you ever shoot it with the gas block back against the shoulder? Did it work?
Yeah it wasnt working against the journal. After moving back like you see in the first picture it seems to be running the same. I might buy those little plastic dowels or the gas block genie to make sure its on there just right.

When charging is the action smooth...does the BGG easily come off the gas tube and seat all the way back in, lugs have rotated, etc.. Neighbor's AR10 was cycling for crap and it was an oversized gas tube causing the BCG to bind.
I have two AR15s and this is my first AR10 so Im definitely not an expert on the platform. My AR15s seem to charge much easier. I just figured that was how its supposed to be? I noticed when I shoot the first shot it almost seems seized up. I dont have to mortar it or anything but it does give me trouble.

Thanks for all the replies fellas, I appreciate it! Ive been buying parts and tinkering with this thing for so long, its disheartening when it doesnt run.
 

Powder_Burns

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Loosen your gas block, stick a foam earplug in your chamber, blow some compressed air in the barrel and move the block around until you can feel good flow out the gas tube. Or take it off, measure and use a pencil to make some witness marks on your bbl and block to ensure its aligned correctly. The journal is for handguard fsb setups, its .025” ahead of that location for an aftermarket block. I would start there. There is also a discrepancy between gas tube lengths for AR-10’s and LR-308 pattern rifles, something else to check.
 

kingofthepoors

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Loosen your gas block, stick a foam earplug in your chamber, blow some compressed air in the barrel and move the block around until you can feel good flow out the gas tube. Or take it off, measure and use a pencil to make some witness marks on your bbl and block to ensure its aligned correctly. The journal is for handguard fsb setups, its .025” ahead of that location for an aftermarket block. I would start there.
Thanks sir! That sounds like a good idea with the compressed air. I might also do the pencil and scribe thing. I just kind of eyeballed it the last few times honestly. Im taking notes of all the suggestions you guys are giving me and will try to knock them all out this week.
 

Ravenworks

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I was running the bcg dry, I had heard from a few places it likes to be ran wet so I sprayed the hell out of it last range trip.
Actually, you need to break the BCG down and oil it properly and make it WET.

The gas block set back is definitely to much, that needs tightened up.

Separate the upper from the lower, slide the BCG by hand, does the gas tube to gas key mating feel tight?
The parts you are using are all quality parts and should play nice together.
New large frame AR's are finicky,believe me.
I own and have built numerous Areo's and they have been exceeding great, never so much as a hiccup on any of them
 
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S197

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have you checked the headspace? Can you post a pic of the spent brass? Are these factory rounds or reloads?
 

Snuby642

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In the picture your gas block adjustment screw looks like it is turned in .
 

bfoosh006

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Sounds like it isn't getting enough gas, and it is a tight / not broken in fit on the parts.

Yes, run the BCG and various moving parts nice and wet for the break in.

And what ammo ? Use full power LC type ball ammo.... Some other ball ammo can be underpowered / the wrong propellant for the gas system.

Break in with the Magpul mag... avoiding the stronger springed Lancer for now.

I would adjust the adj. GB from closed position, a few turns opened, while breaking in. Running it wide open can "cause" other odd issues.... this would also allow some break in of the bolt lugs and receiver extension lugs.

Slowly adjust until the BCG locks back on the single mag loaded round.

And you did clean the chamber prior to firing it ... right ? .... and the receiver extension lugs.

A preservative / rust inhibiting oil in the chamber can make it sticky. And extraction can "stall".

And FWIW.... Large Frame AR's can be considerably more fussy to assm. than AR15's.

And I just read another thread where the gas tube was actually blocked.... so you might check that.
 
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kingofthepoors

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Ok sorry for the delays in my response. I really appreciate all the help from everyone. Ill try to respond to everyone. I was on Reddit the other day and saw a guy had used a bore scope for lining up his gas block. I figured why not and bought one. It came today and Im pretty sure its not the gas block placement. I misspoke saying two credit cards- I meant I spaced it out two business cards. It looks a smidge off and Ill probably fix it but that looks pretty good to me. And not what I believe to be the problem. Snap_004.jpg
*In the picture the screw is probably all the way in or 1.5 turns out (what was recommended to me) I kept adjusting it at the range and it started to eject almost all the way backed out but wouldn't pick up a new round*

*I am not really sure if the gas tube and gas key are too tight. I will take apart the bcg and oil it up good for my range trip tomorrow"

*I haven't checked the headspace with any gauges. The "gunsmith" told me there really isn't an actual spec for AR10s headspace. Sounded wrong but IDK honestly. The tech looked at a inserted cartridge and said I should be fine. Kind f odd they dont have gauges but they are kind of bootleg gunsmiths honestly. The brass seemed fine to me. I am not expert though. But nothing was split or anything crazy. I saved the brass so Ill try to get around to taking a pic*

*The ammo I was using was Winchester Super X 180gr & Federal Power Shok 180 gr. I didnt clean the chamber or anything really. Ill give that a try tonight as well. Im going to try again to get it running tomorrow so Ill update then*
 
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kingofthepoors

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Just got back from the range. I still have a 1500$ single shot rifle! The gas block is 100% aligned. When I shoot a round still won’t eject. When I go to pull back the bolt after firing a round it is almost stuck. It takes a good amount of force to eject the round. This isn’t a problem when I’m operating the gun without firing. Any thoughts? I cleaned the feed ramps. I oiled the hell out of the bolt. I’m thinking it’s either the bolt has problems. The gas tube could be jacked up somehow. Maybe it’s the spring and buffer? Again thanks for the help fellas I really appreciate it. I’m disappointed every time I go to the range. Although to even it out I got some M4 and P90 full auto love to even it out.
 

Snuby642

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Could you borrow another upper for a couple of shots?

That would be s quick way to validate the lower.
A used standard gas block could be found at a gun shop r&r see what happens.
 

bfoosh006

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Can you post some photos of the fired brass cases ? Case rim , head ( and primer and body.

Looking for scratched up cases... from a possible buggered up chamber.

Also looking for the marks from the extractor , popping of the case rim.
 
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clcustom1911

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Or..... your extractor claw might be popping off the case rim whilst the brass is still expanded in the chamber. You may need to tune the gas block to reduce gas flow for possible overgas/timing... or polish your chamber, or both.
 

kingofthepoors

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Here’s all the rounds fired so far. Only got two to eject total. Neither time chambered a new round. Both times was gas almost all the way open. The last pic is a fired round easily fitting into an unified round. I’m not sure if that’s common honestly as I’ve never tried to do that.
 

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*I haven't checked the headspace with any gauges. The "gunsmith" told me there really isn't an actual spec for AR10s headspace.
LMAO yeah that's not right. It sounds like a headspace issue to me. Do you reload at all? I usually make up dummy rounds for test cycling.
 

kingofthepoors

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I dont currently reload but its something I want to get into in the future. I suppose I can buy a no go gauge I just was trying not to if possible.
 

8up

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Curious....did you take any measurements on the fired brass to see if they are close to some fired brass specs? Switch out the gas block to see if it worked?
 

kingofthepoors

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I don’t have a caliper but I might buy one. The gas block is definitely on perfect though as I bought a bore scope for this. They do seem a little expanded though. That might be why it’s harder to extract them.
-edit- after posting I hopped on amazon and bought a cheap caliper. By the time I get this running I’ll have the ultimate set of tools
 

bfoosh006

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Your fired brass looks perfectly normal.... well kind of... ( normal for a bolt gun, Lol ) ... Anyone else notice the complete lack of ejector smear, or typical extractor marks in the photos ?

Those mentioned marks are "the norm" when it comes to even my tweaked Large Frame AR's.

IMHO, that alone implies "no gas, or so danged little that it is meaningless" is making it to the bolt for proper function.

Did you ever check for gas leaks at the gas key ? Or missing gas rings ? .. or a blocked gas tube ?

I am tending to think a blocked gas tube or even the JP gas block ... or something in front of the gas key.

For the OP, and I realize you may not want to hear this.... but I would remove the gas block with the gas tube still installed, look for gas "burn" marks on the barrel, at the gas port ( that will show 100% if the alignment is correct and post PICS ! ;) so we all can see it is properly aligned, and eliminate the slightest doubt. )

Then blow through the shoulder end of the gas tube with the GB, adjusted wide open.

"If" you have another gas tube and GB available compare the 2 against each other.

Using the smooth part of a drill bit , inserted into the gas port.... ( doesn't have to be a perfect fit we are looking for a "this is to big, and that is to small ) let us know what fit and what didn't. That will give us an idea of the gas port size.


How dirty is the upper CH channel ? Looking for normal exhaust gas filth... if the gas is flowing... there should be filth.



Brass wise......No odd scuff marks. So chamber is smooth. Winchester primers look a little flat for my tastes, but ....

The 2 lines on the neck are normal, and will smooth away after enough rounds fired through it.
 
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Billiam1211

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Sounds like a gas block issue for sure. Comment above about cycling some pressurized air may be a great starting point. Also, if you troubleshoot everything to hell and it's still not cycling I'd maybe try and reach out to Ballistic Advantage for a replacement barrel. They're usually really good about it. I've had to return two .308 Win barrels for closing on a No Go gauge. There could be a chance that their gas port is out of spec. If you're gas block is aligned you have the gas open all the way it should be throwing brass a mile away.
 

Snuby642

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I would stop at this point and find a qualified gun smith before something breaks or blows.

You can look up specs on saami. Org

You are having more than normal problems.
 

Powder_Burns

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Verify you have air flow out your gas tube. Fired cases are always going to be harder to extract, they have expanded to fit your chamber. As for bolt/bcg problems, if you take your carrier out you should be able to slide the bolt in and out without unreasonable effort. From the retracted position, just whipping the carrier in your hand should cause the bolt to extend. You would have to have an incredible amount of binding for the gas pressure to prevent the bolt from unlocking. Check the lugs on the bolt and the chamber for any unusual wear, ie shiny marks. If you had a few round actually eject, now you can start ruling out your buffer/spring setup. First thing I would check, pull the charging handle all the way back, see how far the bcg is in the ejection port. With an empty mag inserted, it should lock back on the bolt catch. That will rule out bcg/buffer dimension issues. You may have too much spring going on if you have difficulty pulling the charging handle all the way back. Which buffer tube are you using? A carbine tube calls for a carbine buffer and spring. A rifle tube calls for a rifle buffer and spring. Quick google search will pull up images and measurements for the different systems.
 

celltech

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Still reminds me of my neighbors AR10 with the bad gas tube. When unloaded you could cycle the BCG, but it was stiff. But when fired you had to pile drive it to get the spent shell out. Is it a nickel boron BCG? Could be too much coating in the gas key...
 

Snuby642

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How could the brass contact the lands?
There has got to be some free bore to the chamber or a bullet would stick when he cycled it.
 

Not a Clue

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I don't know if this helps, I'm not qualified to know, but that looks like a rifle length buffer tube, spring, and buffer. I just finished a Aero M5 build and I have the carbine length buffer tube , spring, and buffer. It runs fine. I had to open the gas block almost all the way open to get it to eject and pickup the next shell, but the gun it very tight. I suspect as I get some rounds through it, it's going to loosen up a little and I can probably back the gas down a little. Is that the right buffer tube with that stock? Might be, I'm just asking, but I know mine is all carbine length and it runs fine. Maybe it's as simple as that?
 
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bfoosh006

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Is it me or does it look like the brass is getting shoved into the lands? Maybe the chamber needs to be polished and smoothed out
99% of the time the brass will be scuffed with tell tail visual signs of a rough chamber imprinted on the fired case , and even then, the extractor smear I mentioned would more pronounced... since the case is not freely releasing from the chamber.

Example pic... from the internet

44866258274_454cf73c8f.jpg

As for the brass being shoved into the chamber.... I would suspect the same mentioned "lack of marks" would be clearly visible because of a boast in chamber pressure.
 
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bfoosh006

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I don't know if this helps, I'm not qualified to know, but that looks like a rifle length buffer tube, spring, and buffer. I just finished a Aero M5 build and I have the carbine length buffer tube , spring, and buffer. It runs fine. I had to open the gas block almost all the way open to get it to eject and pickup the next shell, but the gun it very tight. I suspect as I get some rounds through it, it's going to loosen up a little and I can probably back the gas down a little. Is that the right buffer tube with that stock? Might be, I'm just asking, but I know mine is all carbine length and it runs fine. Maybe it's as simple as that?

Your tuning is spot on... but the OP's setup isn't getting enough gas and or certainly not consistently ( he did say he had a few eject. ). Check some of your fired cases, compare them to the pictured ones...I'll bet they are slightly more "abused " ......Lol, If my brass came out of all my Large Frame AR's that pristine , I would be ecstatic.
 
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Snuby642

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New barrel ar.

Nobody at any factory deburrs shit anymore.

Burs, feed ramps like scalpels etc.

Possibly tier one ar barrels are better.

Well they should be.
 
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kingofthepoors

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The gas tube is a stainless Aero rifle length
The buffer, spring and tube are all Luth AR rifle length and supposedly the 308 version. The bolt does lock back on the bolt catch quite easily.
As always thanks again for all the help! Were going to get this thing in action soon I can feel it. I will take it apart and get the requested pics back soon. Ill take the gas block off to verify the size with drill bits. Im having an instructor friend take a look Friday. Hopeully itll be chugging through rounds this weekend.

Not a clue you said you had to have your GB backed all the way out to cycle? Thats what was worrying me as I had saw on a forum that a guy had the JP block on a 308 & 6.5 and had them both backed out 1.5 turns to funtction. I was way over that and didnt want to possibly damage my rifle.
 

Jgunner

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Damn, almost the same build, same problem a guy had at the range just a couple days ago. Feels undergassed. But non-adjustable gas block, but lot of aero parts(barrel, lower and more), but he was missing the green spring in the trigger so it would never reset right unless you were super fast on the trigger.
Had the same buffer setup as well, but a different stock. I wasn’t able to tell what the problem was, but the bolt itself was hard to get to move in the carrier, damn gas rings were sticking pretty far out, nib carrier from black rain or something like that.
 

Not a Clue

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Not a clue you said you had to have your GB backed all the way out to cycle? Thats what was worrying me as I had saw on a forum that a guy had the JP block on a 308 & 6.5 and had them both backed out 1.5 turns to funtction. I was way over that and didnt want to possibly damage my rifle.
I did. I started with it at about 50-60% or so closed. It would fire and eject but not pickup a new round on some ammo. I had 147 grain and 120 grain bullets. For the 120, it would pick up the next round sometimes, but the 147, it would not pickup the next round at all. I opened it up 3/4 of a turn from where it was and it cycled perfectly.

I will say the gun is tight as hell. If you try to manually pull back the charging handle and chamber a round, the bolt won't close if you baby it or are easy on it. You have to pull the changing handle back and let go of it so it slams the load in there. It's all very tight. I'm positive it will loosen up but since it's all new, it's tight as hell. If you baby it and the bolt isn't closed, you can't even close it with the forward assist. It's tight.
 

jwknutson17

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Not a clue you said you had to have your GB backed all the way out to cycle? Thats what was worrying me as I had saw on a forum that a guy had the JP block on a 308 & 6.5 and had them both backed out 1.5 turns to funtction. I was way over that and didnt want to possibly damage my rifle.
If you back the adjustment on your gas block all the way out, this is the best place to start. The same as a non adjustable gas block. So your not restricting the flow from the gas port on your barrel. If your only 1.5 turns open then this is your problem. Open it all the way up. And then tune down as necessary when using a suppressor. Unless the barrels gas port us grossly over sized, you don't need an adjustable gas block unless your trying to tune it down with a suppressor.

Open it up.
 

diggler1833

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I suffered from a completely obstructed nitrided gas tube recently. Put in a new stainless one and away I went. While your issue maybe isn't the same as mine, you may have to start suspecting a faulty part and trouble shoot each of them...which it sounds like your doing.

It's not fun buying a second small part for a build, but sometimes it's necessary.
 
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357Max

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@kingofthepoors - I agree with jwknutson17, open gas block all the way. After that there are some checks that should be done that will not require disassembly.
  • Head space absolutely should be checked. Unless you bought a matched barrel/bolt combo. Just buy the go gauge & buy adding a pc of scotch tape to the back you'll have your no go.
  • Get a piece of weed eater line (bright colored) & slide it from the receiver end all the way in the gas tube, should be visible with bore scope.
  • Remove BCG & remove bolt. Slide weed eater line in gas key (should slide through and be visible in bolt bore.
  • Take your new caliper and measure outside diameter of the gas ring stack. Toolcraft will have 3 rings stacked together and should measure .659 od +/- .002. The ring gaps should be staggered, but it will run with them all lined up or even 1 removed.
  • You said the bolt is stiff in the carrier and that is normal for a new Toolcraft (not crazy stiff, but firm). The ring pack and bore should be oiled with light gun oil or ATF (Automatic transmission fluid).
  • Do you have a Fat wrench? If so put your BCG in a vise, set the wrench for 35 in lbs. Test gas key bolts @ 35 in lbs reverse. If they don't move, it rules out a broken key screw/gas leak. That said look carefully for gas leakage around the key to carrier interface (could have had a metal shaving under key when installed).
  • Per your picture the gas tube appears to be the correct length & set to the correct depth.
  • On a new build I always make sure I can ride the charging handle down slow & it should go into battery without assist. I don't buy into the BS of it's new & tight, but it'll loosen up. If it's right it will smoothly go into battery.
  • Last check. with a empty mag in and BCG on bolt stop, pull BCG all the way back with charging handle. It shouldn't over travel more then about .100 past bolt stop. If it does remove buffer/spring and add quarters to the back of buffer tube to reduce over travel down to .080 - .125 max. This will keep you from breaking the bolt stop & or in extreme cases prevent the carrier from hitting the lower @ buffer tube.
 

Not a Clue

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  • On a new build I always make sure I can ride the charging handle down slow & it should go into battery without assist. I don't buy into the BS of it's new & tight, but it'll loosen up. If it's right it will smoothly go into battery.
Just to be clear, when I made that comment, it was from the standpoint of having a round in it. My build moves freely when there is no round in it. It's tight when there's a round in it. In shooting about 30-40 rounds through it, it's already much better than it was on those first few rounds.