Wont lock back on empty magazine with overgassed upper

[MistWolf]

Well, the new extractor spring was introduced around the same time as the heavy buffer.

I was referring to the extractor spring failures I personally experienced when I was still new to ARs. Some of my early configurations used carbine buffers and generic extractor springs. I suspect carbine buffers led to early failure of those generic extractor springs.

I cannot speak beyond that. I didn't intend to mislead.

[SHERWINVILLARETE]

UPDATE:

Carbine buffer + comm spec bcg = no lock back
H buffer + comm spec bcg = no lock back
H buffer + milspec fa bcg = LOCKED BACK!

Milspec fa bcg 11.5oz
Comm spec bcg 11.2oz

I will try the h2 or h3 next time, test em and call it done.

Ammo:
m193 @ 1-2 oclock ejection
Wolf steel cased @ 3-4 oclock ejection
W/ H buffer + milspec bcg.

This upper actually ran fine with an H buffer and comm spec before. I noticed the lock back issue when i started using the Witt machine SME comp/blast shroud, overgassed an already overgassed upper i guess.j

[Alaska3006]

I use the JP Enhanced Tuned Polished Spring.
I too suggest a H buffer to slow the bolt down.

[Warp]

OP, I had the exact same problem. BCM's are overgassed and it really shows when you suppress some of them, is that the upper in question?

And I had the problem with 20 round 'Colt' magazines (NHMTG), as mentioned in one of the responses, they maybe don't have the strongest springs (might be similar to your old/worn pmags)

Carbine is too light for nearly anything. It's cheap though, so a lot of people run it in their "good as" guns that are overgassed and under weighted and thus "eat everything" while beating shooter and gun to crap but hey at 200 rounds a year who cares?

Somebody mentioned Sprinco blue with H2 buffer. That is well worth trying, lots of positive feedback on that.

But really, Pappabear has it...go intermediate/A5 and never look back. They are in stock everywhere right now, even. Midway, BCM, Primary Arms, etc.