Short stroking caused by BCG

[markm]

I get this on a 14.5 middy that runs 100% suppressed. Gassed lean without the can, but slightly overgassed with the can. So weird. Not a big enough problem to where I've researched it because it's an ACOG setup shot mostly prone/longer distances.

One thing I had happen before is excessive spring tension on the bolt catch.... either due to the detent hole being shallow, or a spring too long.

[TomMcC]

Yes it ran fine in one other AR that I tested it in, but that AR is just gassed higher, so it doesn’t really prove anything. The fact that another BCG cycles properly in the 14.5” upper, is a sure sign that it’s the BCG.

Unless you know what the actual gas port size is, its a guess as to whether a gun is over gassed or not. But be that as it may, do you have another bcg you can try in the present troublesome gun?&

[Todd.K]

An aggressively staked key bolt may be under torqued or even broken in two without the bolt head or key appearing obviously loose.

[Captains1911]

Unless you know what the actual gas port size is, its a guess as to whether a gun is over gassed or not. But be that as it may, do you have another bcg you can try in the present troublesome gun?&

Yes, a BCM BCG I borrowed from another rifle works reliably, locks back every time with the H1 buffer, sorry I should have made that more clear. I even tried the BCM BCG with an H3 buffer, and it locked back 1 out of 2 times, I would have tested this combination more but I was out of ammo at that point.

[TomMcC]

So the upper likes other bcg's and the bcg likes other uppers, but they won't play well together. If you have the the ability to stake gas keys, I would strip the key off, see whats under it, clean under it and remount it and stake it. That, or . just replace the key altogether. You're obviously leaking gas somewhere...maybe its like Clint said through the bolt tail.

[Captains1911]

For what it's worth, this is the BCG in question. I was led to believe that these were regarded as decent quality, it's certainly wasn't inexpensive.

https://palmettostatearmory.com/tool...165449729.html

[MistWolf]

I started having short stroking problems on a high mileage suppressed 11.5" upper.

The BCG related discrepancies were as follows-
- worn gas rings. Installed new gas rings
- leaky gas key. Removed gas key. Cleaned mating surfaces, reinstalled key & staked
- gas tube worn where it fit into the gas key. Installed new gas tube

[markm]

- gas tube worn where it fit into the gas key. Installed new gas tube

This was a problem on mid length gas tubes a while back. I know another member had this happen. I had to change out 2 of them.

Carbon was puking forward in the upper and into the handguard. Couldn't see it until I took the old gas tube out.

[davidjinks]

1 of 2 problems, and I’m pretty sure they’ve been mentioned...

Gas key on BCG

OR

Under gassed gun and some tolerance stacking

[Hohn]

I hope that the Toolcraft NiB bcg I stuck in my last build is gtg. (DD lw 16” middy). Haven’t run it yet. Wouldn’t have been my first choice but with parts availability being what it is, I went with it.

I’d love to get my paws on a REBCG but I’d likely win the lottery first, and I don’t play.