11.5 BCM possible buffer issues

[Animal_Mother556]

I know......I know....another 11.5 buffer question.

The problem is, it seems like everyone has luck with different weights:
"My 11.5 BCM has run perfectly with H"
"BCM specifically designed the 11.5 to run with standard buffers"
"I run an H2 and it is fine"


Anyway...when building my first AR with less than 16 inch barrel I decided to just split the difference and use an H buffer.

Just had her at the range to zero it and out of approximately 50 rounds, I had about 6 of these. Magazines were a mix of older pmags, new generation 20 round mags, and D&H GI mags. Ammo was Independence 55gr 5.56.

I've never seen this particular malfunction with an AR, but my gut says it is a buffer issue. Could it be a break-in issue?

[Animal_Mother556]

What I should have done was load one round in a bunch of mags and check for bolt lock. But I am dumb and forgot....

[C4IGrant]

That ammo sucks. Switch that out first and then try again.

Did you install the GB or did BCM?


C4

[Animal_Mother556]

Alright, I have some other 5.56 I can try.

BCM installed FSB, but I chopped it off pretty much as soon as ai got it. Chopped it without removing it from the gun, which I have done numerous times.

[MistWolf]

Extraction problem. Extractor is losing control of the empty before it can be ejected

[Animal_Mother556]

So, a heavier buffer to slow the bolt down?

[MistWolf]

Replace the extractor spring. Inspect the extractor for damage and wear.

We know it's an extraction issue and not under or over gassing. If under gassed, the rifle would simply not lock back on the last round, or not cycle far enough for clean ejection without stripping the next round from the magazine.

If the rifle were simply over gassed, it would be flinging brass into the next area code. If the excessive carrier speed is causing the extractor to "jump the rim" it's because the spring is weakened but still strong enough to hold the rim during normal speeds. Changing to a heavier buffer may stop the problem, but since the spring is starting to fail, it's only a matter of time until it weakens enough that the problem will return.

Replace the spring and inspect the extractor. I suggest getting the copper colored Colt extractor spring with the black insert. Do not use any kind of o ring. The o ring will place too much tension one the extractor. Last time I checked, Midway had Colt extractor springs for about $5 a piece plus whatever they charge for shipping. Brownell's is a little cheaper, but are on backorder

[Iraqgunz]

All other guessing aside, Federal Independence is way too hot and I wouldn't put it anywhere near anything I own.

You are using too light of a buffer. A BCM 11.5" will run an H2 all day long, and an H3 with good lube and MILSPEC ammo.

[zk556x45]

An extractor spring up-grade and an H2 should resolve this. I've had good luck with the BCM extractor up-grade kits, but MistWolf advises against. YMMV.

[ST911]

Ammo was Independence 55gr 5.56.

There are known and documented issues with the Federal-Independence XM193i. Here is a thread with additional information, including velocities and lot numbers for reference. https://www.m4carbine.net/showthread...ce-5-56-XM193I