Cartridges are bending?

[LMT/556]

1. The rifle is short stroking, when the rounds get bent up the bolt carrier is stripping the round out of the mag, not the bolt face, so the round gets jammed at some high angle with the bolt into the side.
2. I bought 4 NHMTG 20 rnd mags that had the springs in upside down (44 mag kits I bought off of an individual, assembled incorrectly). The rounds would present at bad angles causing a jam.
3. Bolt over base malfunction. Bolt speed is faster than your mag can present the next round (like really over-gassed) due to port or suppressor, buffer too light..

[pinzgauer]

So I'm having the exact same issue and have posted about "ejection route inconsistent" on another thread. Have had the issue for 3 years and Sig had it for 10 days, ground down the M4 feed ramps

Am I the only one that finds this problematic???

Ground through the hardcoat, leaving bare aluminum? Now talk of "polishing" the feedramps?

Something is wrong, they shouldn't have to do that.

[tehpwnag3]

Nope. I felt the same way.

https://www.m4carbine.net/showthread...62#post2765862

Am I the only one that finds this problematic???

Ground through the hardcoat, leaving bare aluminum? Now talk of "polishing" the feedramps?

Something is wrong, they shouldn't have to do that.

[TomMcC]

Am I the only one that finds this problematic???

Ground through the hardcoat, leaving bare aluminum? Now talk of "polishing" the feedramps?

Something is wrong, they shouldn't have to do that.

I think it's more than a bit troubling to use the words "ground down" and "feed ramps" in the same sentence.

Maybe, "lightly polished and took some sharp edges off" will come along soon.

[MistWolf]

1. The rifle is short stroking, when the rounds get bent up the bolt carrier is stripping the round out of the mag, not the bolt face, so the round gets jammed at some high angle with the bolt into the side.
2. I bought 4 NHMTG 20 rnd mags that had the springs in upside down (44 mag kits I bought off of an individual, assembled incorrectly). The rounds would present at bad angles causing a jam.
3. Bolt over base malfunction. Bolt speed is faster than your mag can present the next round (like really over-gassed) due to port or suppressor, buffer too light..

Short stroking will not bend the cases or cause a bolt over base malfunction.

The mag springs have to be really weak for the carrier to out run the mags, even if the AR is grossly over gassed

[LMT/556]

I've seen it first hand. Gas was restricted by a port reducer that relocated itself into the gas tube. The bolt carrier, not the bolt, was stripping the round and it hard impacted either directly into the front of the mag well wall, or at a really steep angle between the mag and feed ramp with the bolt jammed into the side. The offending reducer was removed and it corrected the short stoke problem. Same rifle later a BRT EZTUNE Gas Tube - Midlength was put in to reduce this over gassed noveske 16" mid.

I use two mags at the range, both nhmtg 20 rounders. My mid length LMT MRP when new and with a carbine buffer would occasionally not chamber the next round the first time or so I took it out. I've used these mags many times since without issue. Maybe related, that MRP bolt broke an ejector pin and spilled ejector guts into the feed ramp and crunched the spring, sent it back and LMT corrected it. H2 buffer corrected the rifles cycling behavior, I just forgot to change out the buffer on a new lower. Why LMT uses a carbine buffer is beyond me.

Look at the suppressed rifle that jams with too light a buffer, same issue bolt carrier speed is too fast.

[LMT/556]

https://www.youtube.com/watch?v=q4TMz69Gfs4
While he changed the buffer spring in the video to correct that bolt over base issue, excess carrier speed was causing the feeding issue.

[MistWolf]

I've seen it first hand. Gas was restricted by a port reducer that relocated itself into the gas tube. The bolt carrier, not the bolt, was stripping the round and it hard impacted either directly into the front of the mag well wall, or at a really steep angle between the mag and feed ramp with the bolt jammed into the side. The offending reducer was removed and it corrected the short stoke problem. Same rifle later a BRT EZTUNE Gas Tube - Midlength was put in to reduce this over gassed noveske 16" mid.

I use two mags at the range, both nhmtg 20 rounders. My mid length LMT MRP when new and with a carbine buffer would occasionally not chamber the next round the first time or so I took it out. I've used these mags many times since without issue. Maybe related, that MRP bolt broke an ejector pin and spilled ejector guts into the feed ramp and crunched the spring, sent it back and LMT corrected it. H2 buffer corrected the rifles cycling behavior, I just forgot to change out the buffer on a new lower. Why LMT uses a carbine buffer is beyond me.

Look at the suppressed rifle that jams with too light a buffer, same issue bolt carrier speed is too fast.

Interesting. I played around with an AR set up to short stroke and could not get it to strip a round from the mag unless the bolt came back far enough to catch the rim. I couldn't get the carrier to strip a round, even when I tried by hand.

When I played with a grossly over gassed 10.5" AR, I couldn't get the carrier to out run any of my magazines. I do agree with you that too much carrier speed can cause trouble.

[LMT/556]

In all fairness the bolt may have been catching in the case extractor groove to push the round forward but I don't believe it was fully behind the case when the feed failure occurred.

[tehpwnag3]

OP needs to report back after trying out that new BCG, with both brands of ammo.