PROBLEM SOLVED! - C3 AR lower owners - feeding/cycling issues

[smokymtnsmoke]

Are any of you experiencing feeding/cycling issues?

My build:
C3 lower w/ DPMS LPK, A2 rifle stock/buffer/spring
"Keyhole" on M4 4 year old upper with feed ramps but unknown finisher, 20" heavy barrel, rifle gas tube low profile gas block, 15" Tray Alpha rail, Core15 Nibx BCG w/ nibx hammer

The issue is with all magazines I own, magpul, c products, AR Stoner, Colt. Insert mag, pull charging handle loads round, fire but jams the next round. Either not feeding or round jams at angle. Sometimes misfire with no firing pin mark on primer, clear misfire by cycling charging handle w/ next round firing but the either a FTF/stuck at angle. Mine is a new M4 style upper with ramps. This is more like the round in not sitting high enough to be push forward out of the magazine.

Ammo was my reloads of 55gr SP pills over 25gr of Ramshot TAC that shoots good in my other AR as well as the Saiga.

I have another AR but not with me at today's range session. I'd like to swap that 16" upper on and see if it has the same issue. I'm thinking that either the upper or the C3 lower may be a few thousands out of spec or maybe a weak recoil buffer spring even though it has less than 500 rounds on it.

What's y'alls experience?

 

[Shovelhead]

My experience with C3 lowers (3 of them) to be blunt they are crap. Magazine issues all three with Magpul. Various problems with fitment. I can see why they are defunct. I ditched two at a loss with full disclosures. The buyers have problems as well. The third one I got to work with GI mags. I have too much rolled into it with cerakote and extras I'd lose my ass on it trying to sell or trade.

 

[user 71]

Doesn't sound like a mag issue but rather an issue with your rifles action.

So, the prior round ejects but the next round is a misdeed?

Short-stroking? I would check the gas block alignment to the barrel. It seems like 75% of the time when these symptoms happen, there's a problem with the gas system - usually it's the gas block.

 

[RamRoddoc]

Doesn't sound like a mag issue but rather an issue with your rifles action.

So, the prior round ejects but the next round is a misdeed?

Short-stroking? I would check the gas block alignment to the barrel. It seems like 75% of the time when these symptoms happen, there's a problem with the gas system - usually it's the gas block.

On point...



PMAGs are tight in the magwell and don't drop free. Metal G.I. magazines and Black Dog polymer magazines no issues. C3 machined these to tight tolerances and the magwell could use a bit more wiggle room.

 

[smokymtnsmoke]

I'm sitting here taking measurements with my digital caliper between my MEGA and the C3 lowers with the same 20 round Magpul magazine and nothing is jumping out as they are with in a few 0.000 +/- .0002 of each other. Not enough to seem to matter.

 

[smokymtnsmoke]

Thankfully I had a day off and rifle range 15min from the house.

I have 4 lowers so I started off swapping the upper around, same mags. With ALL lowers the problem was consistent.

So I have 3 uppers. This upper came with a BCG originally. Along the way I "upgraded" to NIBx BCG in this upper. So after realizing I had swapped BCG's sometime back I put the original non-NIBx BCG back in this upper and presto, no more crazy FTF issues. Seems a bit crazy but that was the solution to my issue. The NIBx BCG went into the other carbine AR and functioned flawlessly in that upper as well.

So after thinking back 5 years ago when I got this complete upper I have to assume that this bolt was head spaced, or 'tuned' to this barreled upper.

I'm just very happy that My C3 Lower was NOT the issue.

Thanks for all you helpful insight. :cheers:

 

[user 71]

Glad you got it fixed.

I seem to remember another thread about nibx or other special coating causing issues on a bcg.

 

[LewisBrookshire]

Wild, I would have never guessed it was the BCG causing the issue!