Failure to Feed Issue with AR-10

[SeishiDar]

At a loss with a new build and hoping for some help/insight with a failure to feed issue.

Weapon details:
AR-10 in .308 custom built rifle with Spikes Tactical matched receivers
16" proof research carbon fiber barrel with matching gas tube
Brownell's lightweight titanium CBG
VSeven A5 buffer tube
JP Enterprises captured spring with H2 buffer weights with A5 spacer
Spikes Tactical branded superlative arms adjustable gas block
LaRue two stage trigger
Magpul PRS Lite stock
Sil3ncerCo? 3 port muzzle brake Remaining small parts are VSeven titanium.

Description: Have gas wide open. Using 147 grain ammo (lightest load I will likely use). 9/10 times rifle cycles properly, pull trigger, goes bang. Able to manually lock bolt back.
1 in 10, fails to feed. 9/10 times fails to lock back on empty magazine. Issue is repeatable over 5 different malpul magazines. Tried swapping out from medium to light spring, peoblem continues. Ammo ejects at 3 o'clock with lightest spring, around 3:30 with medium spring. Problems occur at same frequency with both springs.

 

[FredHammer]

At a loss with a new build and hoping for some help/insight with a failure to feed issue.

Weapon details:
AR-10 in .308 custom built rifle with Spikes Tactical matched receivers
16" proof research carbon fiber barrel with matching gas tube
Brownell's lightweight titanium CBG
VSeven A5 buffer tube
JP Enterprises captured spring with H2 buffer weights with A5 spacer
Spikes Tactical branded superlative arms adjustable gas block
LaRue two stage trigger
Magpul PRS Lite stock
Sil3ncerCo? 3 port muzzle brake Remaining small parts are VSeven titanium.

Description: Have gas wide open. Using 147 grain ammo (lightest load I will likely use). 9/10 times rifle cycles properly, pull trigger, goes bang. Able to manually lock bolt back.
1 in 10, fails to feed. 9/10 times fails to lock back on empty magazine. Issue is repeatable over 5 different malpul magazines. Tried swapping out from medium to light spring, peoblem continues. Ammo ejects at 3 o'clock with lightest spring, around 3:30 with medium spring. Problems occur at same frequency with both springs.

Boldened topics:
Never used titanium BCGs, but possible there is not enough mass to give her enough ass to cycle completely?
SA gas bock "wide open" means 18 clicks out? No bleed off yet. Correct?

I'll quote Karl Childers, "It ain't got no gas in it!"

I would drill the gas port .002 larger and let'er rip, tater chip!

 

[SeishiDar]

Boldened topics:
Never used titanium BCGs, but possible there is not enough mass to give her enough ass to cycle completely?
SA gas bock "wide open" means 18 clicks out? No bleed off yet. Correct?

I'll quote Karl Childers, "It ain't got no gas in it!"

I would drill the gas port .002 larger and let'er rip, tater chip!

Full open = 18 clicks/4.5 turns on the gas block so no bleeding.
I would have thought a lighter weight BCG would need less gas to fully cycle as there is less mass/inertia to overcome, especially with a lighter weight spring behind it.

 

[msgriff]

Low mass operating systems (LMOS) do require less gas. Sometimes over-speed is confused with under-gassed, the BCG can outrun the mag spring. The window of proper function is usually narrower than a full mass operating system and will change as the firearm breaks in. I would try turning the gas down and make sure the BCG is well lubed. Also check your bolt to bolt catch clearance at full pull-back of the charging handle.

 

[FredHammer]

Low mass operating systems (LMOS) do require less gas. Sometimes over-speed is confused with under-gassed, the BCG can outrun the mag spring. The window of proper function is usually narrower than a full mass operating system and will change as the firearm breaks in. I would try turning the gas down and make sure the BCG is well lubed. Also check your bolt to bolt catch clearance at full pull-back of the charging handle.

That makes sense. My OG situations, the BCG is moving too fast.

OP:

I guess the brass ejection pattern at the 3:30ish threw me from OG. So, it might go 3:30, but how is its travel in that direction? Do the cases just clear the port and”bloop” out or a healthy straight line, accumulating in a nice little pile?

I’ve also not had the SA gas block work to great as a restrictive gas block. Bleed off mode, they’re awesome. Restrictive not so good that I’ll resort to a typical restrictive gas block. Don’t know why this is the case with the SA.

Anyways, after all that babble. Try 10 clicks out (in restrictive mode)

 

[FredHammer]

Ope, almost forgot. Clocking the brass pattern you might consider 2:45 brass ejection to get 3:30 dirty gun reliability. Or you risk 3:30 clean and unreliable when it goes dirty.

 

[CaptArab]

It seems like 90% of the time people start these "my ar10 doesn't work" threads they've gone all stupid with the lightweight carrier BS.

Use a standard toolcraft large frame BCG with the longest gas system available for your barrel- works great and costs way less. Rifle tube and buffer or 7-5/8 tube with the slash buffer. Proven, simple and cheap.

I don't get why people get all wrapped around the axle spending as much as possible on all the flashy tinker toy stuff. None of the proven mil contract large frames use any of that crap.

 

[CaptArab]

JP stuff is such a joke.

I've wasted tons of money on it but it's stupid.

Unless you want a turn key gamer 9mm PCC, you'd be better off taking the extra cash and lighting it on fire. At least that way you'd only throw away your money, not your time too.

 

[SeishiDar]

That makes sense. My OG situations, the BCG is moving too fast.

OP:

I guess the brass ejection pattern at the 3:30ish threw me from OG. So, it might go 3:30, but how is its travel in that direction? Do the cases just clear the port and”bloop” out or a healthy straight line, accumulating in a nice little pile?

I’ve also not had the SA gas block work to great as a restrictive gas block. Bleed off mode, they’re awesome. Restrictive not so good that I’ll resort to a typical restrictive gas block. Don’t know why this is the case with the SA.

Anyways, after all that babble. Try 10 clicks out (in restrictive mode)

Brass ejection is definitely a strong straight line perpendicular to the barrel and the ground as opposed to a "bloop" that barely clears the rifle/trigger hand.

Will try restricting the gas and see how things turn out.

 

[Huskydriver]

@

It seems like 90% of the time people start these "my ar10 doesn't work" threads they've gone all stupid with the lightweight carrier BS.

Use a standard toolcraft large frame BCG with the longest gas system available for your barrel- works great and costs way less. Rifle tube and buffer or 7-5/8 tube with the slash buffer. Proven, simple and cheap.

I don't get why people get all wrapped around the axle spending as much as possible on all the flashy tinker toy stuff. None of the proven mil contract large frames use any of that crap.

@TonyTheTiger or @bigjake83

 

[BCP]

Check for gas leaks at block. Try a regular spring and a regular buffer, dial back the gas and start over. Or perhaps lighten up the buffer weights and start over with your gas system tuning.

 

[FredHammer]

@
@TonyTheTiger or @bigjake83

Oh God! Summons and rain the pain! Someone said icky things about JP!

 

[TonyTheTiger]

@
@TonyTheTiger or @bigjake83

Oh God! Summons and rain the pain! Someone said icky things about JP!

Not this guy. I'm very much a large frame novice.
I'd be happy to defend lightweight operating systems in small frame guns, but I'm out of my element here. I'm just barely smart enough to mostly stay in my lane on this forum.

 

[Huskydriver]

Oh God! Summons and rain the pain! Someone said icky things about JP!

Had nothing to do with jp was hoping they could shed some light on lightweight builds

 

[MontanaMan]

Low mass operating systems (LMOS) do require less gas. Sometimes over-speed is confused with under-gassed, the BCG can outrun the mag spring. The window of proper function is usually narrower than a full mass operating system and will change as the firearm breaks in. I would try turning the gas down and make sure the BCG is well lubed. Also check your bolt to bolt catch clearance at full pull-back of the charging handle.

^^^^^^^ The bolt moving too fast is my guess as well; with an AGB, I always turn gas down to where the bolt will not lock back, then adjust open just enough to get reliable function.

Just had pretty much the same issue with a new POF 308 that my son bought against my best advice.

MM

 

[papershredder]

To shorten up a long post I had typed out, I'm in agreement with the above that your bolt velocity is too high. You mentioned swapping springs, if you're using the spring kit for the JP SCS, use the heavy spring as it will help further reduce bolt speed. That's all assuming the bcg is clearing the bolt catch like it should. If by slim chance you are undergassed, the other possibilities are gas block not aligned with port, port too small, or leaky gas around the bcg or block as BCP mentioned above.

 

[FredHammer]

To shorten up a long post I had typed out, I'm in agreement with the above that your bolt velocity is too high. You mentioned swapping springs, if you're using the spring kit for the JP SCS, use the heavy spring as it will help further reduce bolt speed. That's all assuming the bcg is clearing the bolt catch like it should. If by slim chance you are undergassed, the other possibilities are gas block not aligned with port, port too small, or leaky gas around the bcg or block as BCP mentioned above.

It's an enigma though. Every BCG I had running too fast didn't straight line eject with any healthy velocity to it. Really no straight line at all and they bloop out, landing about 6" outside the ejection port. Just prior to that OG point condition, the brass typically shoots 1-1:30.

As per the OP: "Brass ejection is definitely a strong straight line perpendicular to the barrel and the ground as opposed to a "bloop" that barely clears the rifle/trigger hand."

 

[mettee]

Your bcg is down on weight from the JP LMOS by 2.25 oz. That is a lot.

In the A5 extension you could try a rifle length spring and a much heavier buffer. You will need to make up some weight, and very likely add quite a bit of bcg/buffer weight. I'm running 8.5 oz with a full mass carrier and rifle length spring both suppressed and unsuppresed...

 

[msgriff]

Brass ejection is definitely a strong straight line perpendicular to the barrel and the ground as opposed to a "bloop" that barely clears the rifle/trigger hand.

Will try restricting the gas and see how things turn out.

Your ejection is fine. Unlike a mil-spec AR-15, ejection angle and distance (within reason) is mostly irrelevant in a large frame. The shell deflector designs and placement can vary greatly between manufacturers. Here's a image of a Spike's ST-10 and an Aero M-5 for comparison:

 

[SeishiDar]

Your bcg is down on weight from the JP LMOS by 2.25 oz. That is a lot.

In the A5 extension you could try a rifle length spring and a much heavier buffer. You will need to make up some weight, and very likely add quite a bit of bcg/buffer weight. I'm running 8.5 oz with a full mass carrier and rifle length spring both suppressed and unsuppresed...

Doesn't this render the use of a LMOS BCG superfluous by adding back all the reciprocating mass?

To shorten up a long post I had typed out, I'm in agreement with the above that your bolt velocity is too high. You mentioned swapping springs, if you're using the spring kit for the JP SCS, use the heavy spring as it will help further reduce bolt speed. That's all assuming the bcg is clearing the bolt catch like it should. If by slim chance you are undergassed, the other possibilities are gas block not aligned with port, port too small, or leaky gas around the bcg or block as BCP mentioned above.

A little counter intuitive going to the heaviest spring to slow things down. I would have thought the lightest spring would be slower with the lower spring constant and therefore expand slower than a beefier spring would. I suppose the slower compression over comes that? Worth a short as well as meddling with the gas after that change.

 

[mettee]

Doesn't this render the use of a LMOS BCG superfluous by adding back all the reciprocating mass?

Yes and no. You are running a BCG with less weight than JP does. You could call JP and see if you can get any info from them, give them your combo and tell them the weights.

It's already been mentioned but you are trying to tune within a very small window where these types of setups perform.

Any change in ammo in the future, and you will be chasing issues again.

 

[bfoosh006]

For the OP, how did it run with the gas restricted more ?

 

[Jsp556]

I don’t know anything about JP parts so I have to ask. Why use an A5 RE and put a spacer in it? Do JP large frames use a standard carbine length RE?

Nvm… I looked it up. The spacer is for rifle length tubes. It says you have to modify the spacer for the Armalite/A5 tube length.

 

[msgriff]

I don’t know anything about JP parts so I have to ask. Why use an A5 RE and put a spacer in it? Do JP large frames use a standard carbine length RE?

Yes, the JP SCS only needs a standard carbine RE on a large frame.
Other than a potential increase in LOP, which is almost never needed on a large frame, the main reason to use an intermediate (A5) RE is so when you finally give up on getting the SCS to work, you're set to go with the better of the two conventional carbine action/recoil systems.

 

[Jsp556]

Yes, the JP SCS only needs a standard carbine RE on a large frame.
Other than a potential increase in LOP, which is almost never needed on a large frame, the main reason to use an intermediate (A5) RE is so when you finally give up on getting the SCS to work, you're set to go with the better of the two carbine action/recoil systems.

Yep. The Armalite/SR-25 is the easy button.

 

[SeishiDar]

Wanted to give everyone an update. Went to an H3 buffer on the JP Enterprises SCS. Worked like a charm for about the first 5 to 10 rounds. Locks back on the last round in a magazine. Once the rifle/barrel/adjustable gas block get any heat to them, it goes back to its old ways. Makes me think that once it warms up, I start to get a bit of gas leakage. With it so close to the function/non-function threshold, this is enough to crap it out with failures to feed and not locking back on an empty magazine.

Thinking of getting a new gas tube for my Proof Research 16" CF barrel and a non-adjustable titanium gas block. No way am I trying to unpin that bastard Hoping the titanium block helps seal things at the barrel as everything warms up with the differential expansion coefficients.

 

[SeishiDar]

For the OP, how did it run with the gas restricted more ?

All the issued were magnified/worse or wven non-functional.

 

[Shoots 700's]

Most ar10 say to run a full weight carrier.

 

[SeishiDar]

Most ar10 say to run a full weight carrier.

This was the solution in the end. With 175 grain Lapua Scenar-L, it would function with an H3 buffer and a titanium bolt carrier (just over 12 oz). It wouldn't lock back or would fail to feed with lighter loads. Changed to a Toolcraft full mass carrier and no issues so far. Need to tweak the gas and possibly go back to an H2 buffer. Kicks off target a lot more now but cycles so take what you can get.

 

[mettee]

What does your brass look like?

 

[SeishiDar]

What does your brass look like?

Like spent brass. Was at an indoor range so didn't pay much attention to ejection pattern since it was bouncing off the walls in every direction and what did bounce behind me was swept away by the overly zealous staff.

 

[mettee]

Like spent brass. Was at an indoor range so didn't pay much attention to ejection pattern since it was bouncing off the walls in every direction and what did bounce behind me was swept away by the overly zealous staff.

It's important, you can learn a lot from examining the spent brass. Ejection pattern is one thing but that's not the main reason for looking at it.

If you don't care, forget I mentioned it

 

[SeishiDar]

It's important, you can learn a lot from examining the spent brass. Ejection pattern is one thing but that's not the main reason for looking at it.

If you don't care, forget I mentioned it

There definitely is. Hence why I mentioned the brass being cleaned up. Next time I'll be able to collect and look at it to learn all the additional details it tells.

 

[Top O' Texas]

I've used many different brands and weighted carriers along with non and adjustable blocks. Try this! Install a full weight group and retry. If it operates reliably then reinstall the titanium carrier, choke the gas 1/3 open, load 3 in the mag and recheck. As mentioned before the carrier might be moving to fast and override the catch. If it's moving to fast it will act like it's double feeding/stove piping. Forgot to ask about gas system length? Carbine or mid? Gas port size is key along with making sure the gas block is properly aligned. If not aligned it WILL cause unnecessary drag on the gas key. Check this way, have carrier under tension and rotate the block or have the carrier out of battery enough the tube alignment causes the gas key to hold the carrier back. Rotate the block until the tube aligns with gas key and under spring pressure it will close. If you have the gun leveled you can see the tube is off center which will tell you the gas block is not aligned. It will also push (or try to) the block toward the muzzle. This gives you a sense of alignment. If you have a borescope you can check for alignment also or remove the upper and carrier and use compressed air (plug the chamber with an empty case as to listen for air at the muzzle. I have 6 AR10's I use light weight carriers in very successfully and DOES reduce recoil quite a bit!

 

[SeishiDar]

I've used many different brands and weighted carriers along with non and adjustable blocks. Try this! Install a full weight group and retry. If it operates reliably then reinstall the titanium carrier, choke the gas 1/3 open, load 3 in the mag and recheck. As mentioned before the carrier might be moving to fast and override the catch. If it's moving to fast it will act like it's double feeding/stove piping. Forgot to ask about gas system length? Carbine or mid? Gas port size is key along with making sure the gas block is properly aligned. If not aligned it WILL cause unnecessary drag on the gas key. Check this way, have carrier under tension and rotate the block or have the carrier out of battery enough the tube alignment causes the gas key to hold the carrier back. Rotate the block until the tube aligns with gas key and under spring pressure it will close. If you have the gun leveled you can see the tube is off center which will tell you the gas block is not aligned. It will also push (or try to) the block toward the muzzle. This gives you a sense of alignment. If you have a borescope you can check for alignment also or remove the upper and carrier and use compressed air (plug the chamber with an empty case as to listen for air at the muzzle. I have 6 AR10's I use light weight carriers in very successfully and DOES reduce recoil quite a bit!

Full weight group works. I can try again with the titanium and the gas chocker down, but before it wouldn't cycle. I tried all three spring weights from JP Enterprises SCS system with the titanium carrier to slow it down but no luck.
I was not not having type III double feeds, just type I, failure to feed. It would be a single round, usually loaded halfway or more.
The gas length is mid length as provided by Proof Research with the 16 inch carbon fiber barrel. Double checked and the gas block is properly aligned as are the keys on both carriers.
Talked with Proof Research (amazing customer service) and they told me they designed their gas port location, size, and journey to maximize and function a full mass carrier, that it's likely to have the failure to feed issues I described with a lighter weight group. They said the BCG does not have enough inertia and starts moving too soon and gets kicked back before full pressure is built up, causing it to short stroke. This is where I went wrong, trying to make the ultralight BCG work with a barrel designed for full mass.

 

[mettee]

I'm really curious about another combo. Your adjustable gas block overcomes the proof barrel being set up for full mass carriers by reducing the gas.

I would also think to maybe try a standard rifle length spring with a 5.3oz A5 buffer with the TI carrier and a gas adjustment like stated above.

That might get it running, but still be cautious of the ammo fluctuation possibly causing changes in functionality.

I think you will see the best results with the rifle spring with either the full mass or the Ti bcgs.

 

[SeishiDar]

I'm really curious about another combo. Your adjustable gas block overcomes the proof barrel being set up for full mass carriers by reducing the gas.

I would also think to maybe try a standard rifle length spring with a 5.3oz A5 buffer with the TI carrier and a gas adjustment like stated above.

That might get it running, but still be cautious of the ammo fluctuation possibly causing changes in functionality.

I think you will see the best results with the rifle spring with either the full mass or the Ti bcgs.

Could be an interesting experiment. May be if I end up with a rifle spring and another buffer. Kinda built myself into a corner with the SCS.

 

[Top O' Texas]

Full weight group works. I can try again with the titanium and the gas chocker down, but before it wouldn't cycle. I tried all three spring weights from JP Enterprises SCS system with the titanium carrier to slow it down but no luck.
I was not not having type III double feeds, just type I, failure to feed. It would be a single round, usually loaded halfway or more.
The gas length is mid length as provided by Proof Research with the 16 inch carbon fiber barrel. Double checked and the gas block is properly aligned as are the keys on both carriers.
Talked with Proof Research (amazing customer service) and they told me they designed their gas port location, size, and journey to maximize and function a full mass carrier, that it's likely to have the failure to feed issues I described with a lighter weight group. They said the BCG does not have enough inertia and starts moving too soon and gets kicked back before full pressure is built up, causing it to short stroke. This is where I went wrong, trying to make the ultralight BCG work with a barrel designed for full mass.

So, the gas port location or gas port size per PR's design? Here's what I came across when using scs. I have some in AR 10's and 15's with and without the rifle spacer. You NEED to check how and how much the scs makes contact with the bcg. It NEEDS to be where you almost have to push the scs back to close the upper. If not, then you need to use the supplied spacer (c-clip) with it or there's just enough gap for a delay. On mine I had to do more tuning to get the scs to work. I'm curious about the port size in relation to the mid length? Aero Precision (which I've had amazing results with) uses a mid-length gas on their 16" with .073 port. Per PR's statement about it doesn't have inertia to start moving is preposterous as it wouldn't take as much gas to start being lighter (bcg). If your reason for using a Ti carrier is for reduced recoil (which is fine) I usually need a heavier spring (not the flat ground) and sometimes a heavier buffer depending on ammo.

 

[msgriff]

I'm really curious about another combo. Your adjustable gas block overcomes the proof barrel being set up for full mass carriers by reducing the gas.

I would also think to maybe try a standard rifle length spring with a 5.3oz A5 buffer with the TI carrier and a gas adjustment like stated above.

That might get it running, but still be cautious of the ammo fluctuation possibly causing changes in functionality.

I think you will see the best results with the rifle spring with either the full mass or the Ti bcgs.

You can't use an A5 buffer (~4.2"). The correct buffer is an AR-15 carbine buffer (3.25") for a AR-10/308 short action using an intermediate (A5) length RE. Although using a rifle length spring is generally correct for that RE, there are some exceptions, like KAC and LMT, who have different springs for their rifle and carbine 308 actions.

OP, just to clarify, you did cut down the JP SCS spacer as mentioned previously in post #23?

 

[mtrmn]

Yes, the JP SCS only needs a standard carbine RE on a large frame.
Other than a potential increase in LOP, which is almost never needed on a large frame, the main reason to use an intermediate (A5) RE is so when you finally give up on getting the SCS to work, you're set to go with the better of the two conventional carbine action/recoil systems.

For RELIABILITY, ^^THIS is the way. ^^ coupled with a full weight BCG. The kit below comes standard with a 5.4 oz H3 buffer, the best starting point (IMO) for large frame builds. The lightweight large frame AR is a noble goal, but In my experience the sacrifice of total reliability for the sake of weight savings is just too high a price to pay. The window of proper function is just too narrow with the lightweight systems to allow for any changes in ammo or conditions. I currently have a Heavybuffers.com 8.5 oz buffer/Armalite rifle spring in mine coupled with an AGB. That buffer can be disassembled and the tungsten weights can be swapped out with regular steel weights to create at least 3 more weight combinations. My 16" .308 AR is not light, but the recoil is, and it's now reliable after a long journey of making a PSA build work properly. I'm not trying to tell you what to do, you're as free a man as any of us nowadays. This all just my opinion based on prior experience, and it's worth every cent you paid for it. YMMV

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[SeishiDar]

So, the gas port location or gas port size per PR's design? Here's what I came across when using scs. I have some in AR 10's and 15's with and without the rifle spacer. You NEED to check how and how much the scs makes contact with the bcg. It NEEDS to be where you almost have to push the scs back to close the upper. If not, then you need to use the supplied spacer (c-clip) with it or there's just enough gap for a delay. On mine I had to do more tuning to get the scs to work. I'm curious about the port size in relation to the mid length? Aero Precision (which I've had amazing results with) uses a mid-length gas on their 16" with .073 port. Per PR's statement about it doesn't have inertia to start moving is preposterous as it wouldn't take as much gas to start being lighter (bcg). If your reason for using a Ti carrier is for reduced recoil (which is fine) I usually need a heavier spring (not the flat ground) and sometimes a heavier buffer depending on ammo.

Size and location of the gas port. Port size is .086. PR's gas port location is further down the barrel. The gas tube is an intermediate (not mid, my mistake earlier) and 13.75" and a 16" barrel.

I'm using the A5 buffer tube spacer I bought from JPE for the SCS with an A5 tube right now. Will double check the spacing to make sure there is no gap.

I apologize if I was not clear. It's the opposite of not enough inertia to move it. The BCG does not have enough inertia to RESIST moving too early. Therefore, the BCG begins moving back with less gas pressure and the key separates from the gas tube before full/enough pressure is built up to throw the BCG all the way back. Hence, short stroking.

 

[SeishiDar]

For RELIABILITY, ^^THIS is the way. ^^ coupled with a full weight BCG. The kit below comes standard with a 5.4 oz H3 buffer, the best starting point (IMO) for large frame builds. The lightweight large frame AR is a noble goal, but In my experience the sacrifice of total reliability for the sake of weight savings is just too high a price to pay. The window of proper function is just too narrow with the lightweight systems to allow for any changes in ammo or conditions. I currently have a Heavybuffers.com 8.5 oz buffer/Armalite rifle spring in mine coupled with an AGB. That buffer can be disassembled and the tungsten weights can be swapped out with regular steel weights to create at least 3 more weight combinations. My 16" .308 AR is not light, but the recoil is, and it's now reliable after a long journey of making a PSA build work properly. I'm not trying to tell you what to do, you're as free a man as any of us nowadays. This all just my opinion based on prior experience, and it's worth every cent you paid for it. YMMV

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Thank you for the link and insight. This is my first build so a bit of a journey.

 

[mettee]

You can't use an A5 buffer (~4.2"). The correct buffer is an AR-15 carbine buffer (3.25") for a AR-10/308 short action using an intermediate (A5) length RE. Although using a rifle length spring is generally correct for that RE, there are some exceptions, like KAC and LMT, who have different springs for their rifle and carbine 308 actions.

OP, just to clarify, you did cut down the JP SCS spacer as mentioned previously in post #23?

Good catch, and you are correct. I forgot we are talking ar10.

The only reason I am suggesting the rifle spring combo is because I have seen nothing but issues with the jp spring.