AR15 Feed Issue

[GUNNER75]

Oly LTF upper, Oly lower with Timney Trigger, some other goodies, but mostly a stock rifle.
Ammo used=HSM 50gr V Max

No issues what so ever for 500 to 750 rounds.

Installed suppressor, have run 150 rounds here and there with suppressor and same ammo. Last time shooting with suppressor, I had a couple 2nd round jam's. Charge rifle=no issue, Fire rifle=first round eject, second round jam.
Round is 1/2 up feed ramp and the bolt has ran into the case at mid point creating two heavy dents from bolt lug to case contact.

Cleaned rifle really really well, checked gas port, alignment, etc. Cleaned steel 10 round mags, lubed all well.

Next time out, no suppressor. Gun operated w/o issue for probably 20 to 25 rounds. Same issue as above, bolt closes on second round and dents case severely.

Ordered P Mags and the M4/CAR15 buffer springs from Tacticalsprings.com.

Everything else with the gun seems to function w/o issue and appears to be in good working order. I am guessing the mags are probably the biggest issue if not the only issue.

Any suggestions?

Once again, gun functioned w/o issue prior to running the suppressor and even the majority of suppressor use. All of the sudden, second round jam.

 

[deadly0311]

Re: AR15 Feed Issue

most likely the magazines fault. Thats the easiest fix for an AR platform is the mags. They are the weakest link in the system

 

[9H_Cracka]

Re: AR15 Feed Issue

It is over riding the round after it partially picks it up. I'd be suspect of the mag. Try a new or very good used condition USGI 20 or 30 rounder and see what it does.

 

[GUNNER75]

Re: AR15 Feed Issue

I installed the Tactical Springs Car15/M4 std weight reliability kit (noticeably different just by charging round) and loaded up a P mag.

Definite change.

Charged rifle, pulled trigger. Rifle is now short stroking, no jammed round. Spent shell is ejected, but second round not picked up.

Thinking back about cleaning this rifle, and while installing the ejector spring included with the Tactical Springs Reliability kit, I noticed that the 3 gas rings on the bolt seemed like they were not quite spread enough, collapsed if yo will.

Stopped by a friends house and picked up a used bolt. Going to swap the three gas rings and test for change. Pretty sure this is my problem at this point from looking at the bolt I picked up. While placing a Brownells order, I picked up a couple McFarland one pc bolt gas rings to have on hand.

Everything else checks out with the gas system and or appears to at this point.

 

[jwn8552]

Re: AR15 Feed Issue

I think you are on the right track. I had a rifle doing this once and I initially thought the mags were the problem. Turned out I needed to replace the gas tube.

 

[salmonaxe]

Re: AR15 Feed Issue

Did you check the carrier's gas key? They can come loose(if not properly staked.) and cause short stroking.

 

[GUNNER75]

Re: AR15 Feed Issue

Well, I overlooked something. When this first happened, I had cleaned the rifle up a bit when checking it over. I put a wrench on the gas key, but didn't put a lot of pressure on it. Just didn't want to break the stake to bolt head contact if it wasn't loose. Should have given it just a bit more umph.

After trying a couple different ring set ups tonight, I thought I better re check the staked key. Sure enough, the front was loose, and the back was slightly snug. Gave them a good pull with the wrench and retested.

Rifle ran w/o issue what so ever, even after running a very loose set of gas rings on the bolt.

Thanks for the assistance fellas.

 

[salmonaxe]

Re: AR15 Feed Issue

Glad that worked out for you. Just FYI, if they're staked like this they're GTG.

They're not properly staked if done like this:

Or like this (Field stake):

Or even this (Light stake):

Since yours came loose, I'm willing to bet that it was done the wrong way. I'd try and see if anyone in your area has a carrier key staking tool. Takes very little time and is great for fixing these little buggers.

Oh and from my experience I've seen in person probably 15 different cases of carrier keys coming loose and causing short stroking. Next big thing on the list was people with setscrew gasblocks having them move because the barrel wasn't dimpled, so they moved forward over time with recoil. (And potentially gas pressure)