BCM Upper/Lower Buffer Weight

[Scott2501]

Hey guys,

I am working on putting together my 2nd AR. I already have a BCM lower, and a BCM upper is on the way. The upper I ordered is a 16" mid-length.

My question is about buffer weight... The BCM lower is marketed as a "M4" lower, so it would make sense for them to include an H buffer, as M4s use the carbine length gas system. However, I will be using a mid-length gas system, as well as a BCM auto bolt carrier.

So, with the lower gas pressure of the mid-length system and the heavier (than semi) auto bolt carrier, is an H buffer still the right choice?

Thanks for any input. Just want to make sure I have my rifle set up correctly.

[ForTehNguyen]

its kinda weird I have two rifles both with midlength gas systems, auto BCGs, H buffers. However one of them ejects casings too late around 2 oclock and one of them ejects perfect at 4oclock. So I swapped the 2oclocker with a carbine buffer to bring it back towards 3-4oclock. The 2oclock was using a spring I got from G&R. Only reason I could think of why they were different. H buffer is a good starting point.

[dialM4murder]

Ive got the same question. Id say the standard weight should be fine. The Colt 6920 I believe ships with an H buffer. So with less gas, Id say a standard weight would be fine??

[Belmont31R]

Both my of BCM middy's run great, and are soft shooting with a standard carbine spring, and H buffer.

[TehLlama]

H should get you in the ballpark, and very marginal price increase over the CAR buffer.

[Showbart]

Both my of BCM middy's run great, and are soft shooting with a standard carbine spring, and H buffer.

This is what BCM recommends with good milspec ammo. Otherwise, if you feed it lower pressure ammo, they say use a CAR buffer.