What do you make of this?

[cast1]

Buddy of mine had some guy build an ar308. He snot it the first time after letting it sit the first time. Builder is out of reach. I haven’t shot it yet. It’s stove piping and trying to feed a round. Apparently it was really jammed and sounded like an over riding bolt. Here’s a pic of the buffer tube when I took the upper off:

it looks like the lower ears on the bolt carrier are slamming into the lower. Any immediate thoughts?

thx
Brian

 

[D̷e̷v̷i̷l̷D̷o̷c̷A̷Z̷]

You think the BCG is wider than the buffer tube or it’s getting off axis?

Idk what happening. But curious to learn form this opportunity.

Can you cycle the BCG w the charging handle?

Also, what kind of Frankengun parts is he using?

 

[sleeplz]

308 doesnt have the mil spec interchangeability that AR 223s have. Gotta get the correct bolt carrier group for that lower/upper.

 

[cast1]

Is it a DPMS/Armalite thing?

 

[iashooter]

308 doesnt have the mil spec interchangeability that AR 223s have. Gotta get the correct bolt carrier group for that lower/upper.

Yep. This is a good and brief article for those that don't realize that not all 308 bcg are the same.

308 Bolt Carrier Group | AR10 Bolt Carrier Group | AR 308 BCG | 308 AR

AR10, AR-308 and 308 AR .308 Bolt Carrier Groups are available in several design variations Armalite AR-10, 308 AR, RRA and POF. They are not interchangeable. Use our detailed guide to explore options and determine the best .308 Bolt Carrier Group for you to buy and use with your rifle

308ar.com

 

[pmclaine]

Is it a piston gun. Carrier being pushed down rather than straight back.

 

[bfoosh006]

Check / measure the buffer tube depth, the buffer OAL , and the how much over travel your BCG has.

The 2 dominate buffer "patterns" use some non-interchangeable parts.

This show some of those differences.
https://www.ar15.com/forums/industr...buffer-system-length-on-the-PA10-/301-286585/

Check to see how much your bcg can actually fully bottom out into your assm. buffer / recoil setup. With the BCG fully depressed into the assm. buffer tube setup, there should only be about 3/16" of a gap between the bolt catch and the bolt face.

What brand lower / what "Generation"

If the buffer / recoil setup is "wrong" ... your battering can result. Most times it is a simple fix.

Please provide descriptive info on the parts used , including basic OAL measurements. Stuff like "2.5" OAL buffer, 3.8oz... in a AR15 carbine buffer tube."

 

[2aBaC̶a̶]

By chance a carbine buffer in a rifle buffer tube?

Either way the tube/buffer/spring combo is wrong and the BCG is going too far back.

Redneck fix is a wrap a bunch of washers or quarters in electrical tape and stick inside the buffer tube before the spring until it doesn't hit.

Coreect fix is get the right parts.

 

[KYAggie]

I agree with 2aBaCa, bolt carrier going to far back. Increase weight of buffer, get a heavier spring, or get an adjustable gas block and tune it until it doesn’t hit. AR10’s are notoriously over gassed. All of mine have an adjustable gas block so I don’t have to add weight in the form of a heavier buffer.

 

[hlee]

Measure the buffer length. The bolt carrier should not be able to hit the lower receiver like that with a correct buffer.

 

[amymorgan20]

I'd at least debur those carrier hits

 

[mtrmn]

Doing some research here will help you out. There are links within these linked pages that it pays to follow too. Proper springs, buffer length/weight, gas tube length, gas port diameter etc all work together to make a properly functioning weapon. The main HMFIC over there can be an A-hole but he knows WTF he's talking about. A lot of this info has already been suggested but these links pretty much explain it all in one place.

Gas tubes, barrel gas ports, and buffer weight

This might end up as a long thread, but it shouldn't be too long. It's a lecture, or a sermon, depending on how you look at it, and I'm not looking for feedback on what I'm about to say. I'm publishing information. In reality, it's pretty damned simple, but manufacturers are making it difficult f...

forum.308ar.com

Buffers and Springs

Do not use AR-15 buffers and springs in a 308 AR. These parts are 308 specific.Either use what your rifle manufacturer would supply or visit heavybuffers.com for aftermarket buffers and technical info.Click here for Buffer SpringsClick here for Tubb Superior Shooting Systems Flat Wound SpringsCli...

forum.308ar.com

Solutions to common .308AR platform problems

This thread pretty much hits on all the common problems in the .308AR platform, when dealing with non-factory rifles. Parts from all kinds of aftermarket manufacturers, that dip their toe in this pond - with no set standard to follow. Inside this link, are other links - this link branches off int...

forum.308ar.com

 

[sheepdog697]

308 doesnt have the mil spec interchangeability that AR 223s have. Gotta get the correct bolt carrier group for that lower/upper.

This was my exact thought....

 

[Maxduty]

My GII PSA did that. AR10s tend to be over gassed just to make sure they run. Usually an adjustable gas block and some tuning of the spring/buffer weights will take care of it. Not an uncommon problem in AR10s from my understanding.

 

[Yondering]

I agree with 2aBaCa, bolt carrier going to far back. Increase weight of buffer, get a heavier spring, or get an adjustable gas block and tune it until it doesn’t hit. AR10’s are notoriously over gassed. All of mine have an adjustable gas block so I don’t have to add weight in the form of a heavier buffer.

Correct problem, but wrong solution. I’ve seen this before and the cause is simple - He has the wrong combination of buffer and buffer tube. This happens when someone uses a short 308 buffer in a long 308 tube; the rifle needs one or the other but not both. Short 308 buffer goes with a standard carbine tube, or standard carbine buffer goes in a long 308 tube.

Combining both 308 parts allows the carrier to travel too far to the rear, causing the damage seen and likely some sticking, which will cause malfunctions.

Easiest solution is to just put a standard carbine buffer in it and verify correct bolt travel. That’s all there is to it.

 

[Bigtrucknut]

Easiest way to check for correct buffer/buffer tube length is to separate the upper from the lower, remove the BCG, and insert it against the buffer/spring into the buffer tube until it stops. If the BCG/buffer bottoms out in the buffer tube with about a 1/4" before the BCG strikes the lower receiver/buffer tube then the buffer/buffer tube/spring lengths are good (see photo). If the BCG strikes the lower receiver/buffer tube (like it does in the OP's photo) then the buffer and tube are incompatible (mix of AR15, AR10/LR308, or A5 buffer system parts).

 

[mtrmn]

OP needs to measure inside depth/length of the buffer tube/receiver extension. Then work from there. If the tube is 7" deep inside it has a std AR15 buffer tube. That takes the 2.5" buffer.
If it's longer, like 7 5/8"(working from memory here), it requires the standard AR15 buffer length of 3.25".
Either way, the buffer needs to weigh ~5.4 oz. (H3) The spring is proprietary to .308 as well. A regular AR15 spring will NOT work on .308.
If he wants it RIGHT THE FIRST TIME he can get the ARMALITE brand buffer/tube/spring kit for AR10 carbine.

AR10REKIT01​

OR go to Heavybuffers.com and Slash will get him straight.
There are still other problems that could exist as well, but this will fix the BCG hitting the lower receiver at the buffer tube.

 

[Yondering]

OP needs to measure inside depth/length of the buffer tube/receiver extension. Then work from there. If the tube is 7" deep inside it has a std AR15 buffer tube. That takes the 2.5" buffer.
If it's longer, like 7 5/8"(working from memory here), it requires the standard AR15 buffer length of 3.25".
Either way, the buffer needs to weigh ~5.4 oz. (H3) The spring is proprietary to .308 as well. A regular AR15 spring will NOT work on .308.
If he wants it RIGHT THE FIRST TIME he can get the ARMALITE brand buffer/tube/spring kit for AR10 carbine.

AR10REKIT01​

OR go to Heavybuffers.com and Slash will get him straight.
There are still other problems that could exist as well, but this will fix the BCG hitting the lower receiver at the buffer tube.

Eh, don’t go so hardline about that stuff. The guy in the links you posted earlier has some good facts, but plenty of garbage too, and there are more right ways to do things than what he claims or what Armalite developed.

308 ARs can run fine on lighter buffers, springs, and carriers as long as the system is balanced. Regardless none of that is the immediate issue with the OPs rifle.