What the heck is going on here?

[spike camp]

A friend told me he traded some labor for a AR platform 6.5 creedmoor.

I haven’t had a chance yet to check out the rifle, but my friend said the casings were showing some markings.
I didn’t know the severity until last night when I received these pics…

 

[Pilsner]

Following. A buddy's AR in 6 ARC is doing nearly the same thing. We have fiddled with the gas settings to no avail
Hoping this thread will generate ideas.

 

[HandgunHTR]

Looks like the rounds are sitting high either due to the feed lips being opened up, or the mag is sitting high and the bolt is running over the rounds as it closes.

 

[spike camp]

Looks like the rounds are sitting high either due to the feed lips being opened up, or the mag is sitting high and the bolt is running over the rounds as it closes.

Thanks for the input.
I was thinking under-gassed, and the reason for the long lug marks. Called bolt over ride?

Mag issue makes sense.
Any input on how to check for mag feed lip height across different brand mags?
I do know my buddy has a different mag he hasn’t tried yet.
Thanks for your thoughts.

 

[HandgunHTR]

Thanks for the input.
I was thinking under-gassed, and the reason for the long lug marks. Called bolt over ride?

Mag issue makes sense.
Any input on how to check for mag feed lip height across different brand mags?
I do know my buddy has a different mag he hasn’t tried yet.
Thanks for your thoughts.

The easiest way to check for mag issues would be to insert a full mag and then use the charging handle to cycle through the mag. Insert, drop the bolt via the release, pull the charging handle and let it go (don't "ride it home"). If your bolt gets hung or rides over the round, it could be that issue.

I would continue to do the above, changing one thing at a time until you can run through a whole or partial mag without issues, then move to shooting it. If it only does it when shot, then the gas or buffer systems can be tinkered with until it gets sorted.

 

[TaperPin]

If all magazines do it, is the mag release holding the magazine up high enough?

If it’s an under gassed bolt issue and it’s adjusted all the way or not adjustable I’d check that the gas hole is aligned and not partially blocked. Measuring clearance of the gas/carrier key might show a source of excess gas loss. Are these low pressure starting loads or does it even do it with factory ammo?

If it’s gassed ok and the bolt is struggling to function is the buffer too heavy or a weird spring. Does the bolt retract fully to the rear or is it stopped by an overly long spring (rifle length spring in carbine buffer tube)? Is it a weird extra heavy bolt carrier group?

With all the mis matched parts guys use to assemble rifles it’s amazing they function at all.

 

[spike camp]

If all magazines do it, is the mag release holding the magazine up high enough?

If it’s an under gassed bolt issue and it’s adjusted all the way or not adjustable I’d check that the gas hole is aligned and not partially blocked. Measuring clearance of the gas/carrier key might show a source of excess gas loss. Are these low pressure starting loads or does it even do it with factory ammo?

If it’s gassed ok and the bolt is struggling to function is the buffer too heavy or a weird spring. Does the bolt retract fully to the rear or is it stopped by an overly long spring (rifle length spring in carbine buffer tube)? Is it a weird extra heavy bolt carrier group?

With all the mis matched parts guys use to assemble rifles it’s amazing they function at all.

Great info, I’ll have it in my hands in an hour.
Appreciate the input, all makes sense.

I believe all ammo is factory, full power rounds.

 

[spike camp]

The easiest way to check for mag issues would be to insert a full mag and then use the charging handle to cycle through the mag. Insert, drop the bolt via the release, pull the charging handle and let it go (don't "ride it home"). If your bolt gets hung or rides over the round, it could be that issue.

I would continue to do the above, changing one thing at a time until you can run through a whole or partial mag without issues, then move to shooting it. If it only does it when shot, then the gas or buffer systems can be tinkered with until it gets sorted.

Thank you again for your input.

 

[spike camp]

Rifle brand is BCA

Turns out those long marks in the third pic were apparently from the feed ramp, and not bolt over ride, or whatever it’s referred to as.

The gas block was off center a hair, straightened that.
The gas tube looked a little short to me…receiver end of gas tube was about <1/3 into that scalloped recessed area.

The mag release was after market and didn’t allow the catch to fully recess when pushing mag release button, wearing the shelf down on the metal magazine a little bit, possibly allowing the mag to sit slightly lower than usual?

The feedramps looked like an old chainsaw blade lol.
We’re going to polish those up and see what happens next time at the range.
Thanks again for the input!