AR having feeding issues

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Encoreman

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Hi guys I need a little help. My son in another state has an issue with an AR in 5.56/.223 and has tried several things. He has cleaned this thing spotless, has had others look at it and they can't seem to figure out the issue. He can shoot 5 or so rounds and the gun will jam with the round bent at chamber. He said he has tried multiple mags and same affect. He is trying to find a gunsmith local to him, but I thought someone may have some things for him to look at. I think this is a Bushmaster, but am not sure. Thanks for any ideas. Mac
 
Magazine.

My 300blk builds lack reliability, the same way. Bolt over brass, dented round. I can build a 556 AR perfectly, while drunk and blindfolded. But the odd rounds, always have odd issues.

Make sure the last round from the mag locks the bolt back. If not, its undergassed. Which is very rare now.
 
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Just for clarification, the previous fired case ejects and the next one fails to feed by jamming while going into the chamber?

Where are the previous rounds ejecting, ie 1,2,3,4,5 or 6 oclock and what kind of feed ramps does ithave? Also the lock back test mentioned above is a good data point.
 
previous 2 responses, I have to check with him to find out. He works all the time and has little time to play. He has never shot this very much that I know. Thanks guys, I will gather more info and check back.
 
It's either undergassed, or it has the wrong buffer. I've seen it where gas blocks leaked, gas ports were plugged with black oxide crystals, or I've seen it where the gas rings on the bolt were bad or lined up wrong. I use JP gas rings now on all my AR stuff.
 
JCooperfan1911:

I feel sorry for so many people -- some with new, good quality brands-- who have problems with their new rifles ( ARs ).
And they arrived brand-new,…not as components to be assembled.

Some people ( I know a couple) ...might possibly....have irrational anxieties about the unknown factors of the shipping process- to the factory for a free diagnosis, or free replacement.
It's better to have very costly paperweights instead of doing what must be done to solve a problem.
 
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AR's are a finicky lot. I once searched and searched and found one little screw on the bolt head that needed tightened just the tiniest bit to allow the gun to cycle properly.....
 
I had a new upper w bcg that the bolt bore was not concentric to the upper. Had terrible feeding issues. A new bcg was the fix.
 
Start simple: is this the first time he has shot it, or did it work fine before and this is a change in operation. Also very helpful to know if is it a new factory gun, a new one assembled from parts, or a used gun either factory or home build. Next thing is ask if anything was added or changed on the gun before he shot the gun and got these results (buffers, springs, triggers, etc.).
 
Hokkmike said:
AR's are a finicky lot. I once searched and searched and found one little screw on the bolt head that needed tightened just the tiniest bit to allow the gun to cycle properly.....
Click to expand...

What screw on the bolt head of an AR-15 would that be?
 
best advice is to return it to stock. AR's feed entirely from the magazine, and its a straight shot. There's no feed ramp, no geometry, nothing much going on. The barrel has a feed ramp, but it would have to be really screwed up to be that bad.

Mechanical issues to consider
Too much buffer weight -pretty much always from taking internet advice.

Damaged/defective bolt lugs -warranty issue, or drop in replacement

M4 feedramped upper with non ramped barrel. -This would be easy to identify, look up "m4 feedramp compatability" on any search engine. Fixable, but a new barrel would be the easy route.

Magcatch in wrong location -usually an issue with 80% lower.

Something not right in the buffer tube, like a bend, or the catch not clearing the bolt channel.

Extreme overgassing. Is the brass more than 20' away? If so, that could be it.

Generally bad alignment of parts is always possible but I would put money on one of the above.

If he can find another AR, the universal diagnosis is get the two together, start swapping upper/lower and test fire.... then bolt carrier group.... then bolt.
If the lower's the problem, you can look at things like mag catches.... buffer..... trigger (bind up/pin problems)
You can pretty well track down failure in a few boxes of ammo.
 
Hokkmike said:
AR's are a finicky lot. I once searched and searched and found one little screw on the bolt head that needed tightened just the tiniest bit to allow the gun to cycle properly.....
Click to expand...

AR's aren't finicky... crummy Colts made in the 1960's while the Army Ordnance department was both setting the specs AND actively sabotaging the design can be finicky....
Proven pretty well by the way the Taliban Flocked to the A2's and M4's we left in Afghanistan.

And there is no screw in the bolt. The only screw in the design holds the fixed stock on.
I think your describing an aftermarket screw type adjustable gas block. That IS a thing but not something a normal AR will have.
You may also be talking about a set screw, or clamp type gas block. This can also cause these issues, a loose screw can bleed gas, if its junk, or slip and cut off gas. But the normal A2 gas block, and a properly pinned (every good manufacturer will tell you pin a gas block) will not have this problem.
 
mjsdwash said:
AR's aren't finicky... crummy Colts made in the 1960's while the Army Ordnance department was both setting the specs AND actively sabotaging the design can be finicky....
Proven pretty well by the way the Taliban Flocked to the A2's and M4's we left in Afghanistan.

And there is no screw in the bolt. The only screw in the design holds the fixed stock on.
I think your describing an aftermarket screw type adjustable gas block. That IS a thing but not something a normal AR will have.
You may also be talking about a set screw, or clamp type gas block. This can also cause these issues, a loose screw can bleed gas, if its junk, or slip and cut off gas. But the normal A2 gas block, and a properly pinned (every good manufacturer will tell you pin a gas block) will not have this problem.
Click to expand...

Maybe he's talking about a gas key screw.
 
GNP said:
Maybe he's talking about a gas key screw.
Click to expand...
Yes, I forgot about that one. Another thing that should never have an effect if the rifle was made right, and certainly not something that requires adjustment/tuning. I forgot those things existed because even the low end brands of been tightening/staking for years now. But I do remember that was a common complaint in the early 2000's.
You also reminded me that these things exist.
https://www.wingtactical.com/firear...nlike a gas block, the,to lock-in the setting.
 
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