Different Gas Lengths, Different Buffer Weights?

AR/M4 AR Technical Discussion
1

I recently upgraded my uppers and replaced several that were older (10+ years), with new uppers from Bravo Company.

My question is around the various barrel lengths and the gas systems and which buffer to choose. I thread a found about this but it was 15 years old…

What’s the consensus for buffer weights for?

​BCM MK2 SS410 18" Rifle length
​BCM MK2 BFH 16" Mid Length
BCM MK2 BFH 14.5" Mid Length

I have Carbine, H, and H2 buffers I think I might even have an H3 somewhere. I couldn’t tell the difference between an H and an H2 in the 14.5"

Thanks,
Cam

2

I run H2 in about everything; 11.5” to 18”.
I run 5.56 pressure ammo, as opposed to “PMC Bronze” type loads.
If I had just received the 3 uppers you list, I’d grab ammo intended for each upper, the H and H2 buffers and head to range and see what works with what; ammo/upper/buffer.

3

Same, I would start with H2 and adjust from there based on performance.

There seems to be too much variability in gas port size to make accurate recommendations on lengths alone.

Bcms longer barrels generally seem gassed correctly, but my 11.5" was way overgassed. It cycled 223 with a wolff xtra power spring and an h3 and was still gassy. Brt ez tune tube fixed it.

4

As recommended, start with some H or H2 buffers and adjust from there. The gas port size is going to play a large role in the correct buffers and spring weights, and each upper could perform differently than the other, even with the same length gas tubes.

5

I also run H2 in everything, so I’d start there with lockback tests on cold days with the weakest ammo you’ll use.

6

I am about to start the same testing on my BCM 14.5. would love to hear what works for you, as my testing is a few months out still.

I have an H and H2 lined up for testing but was also going to be testing with a suppressor on the end.

7

I am sold on Vltor/BCM A5 buffers. I don’t even know the what their standard weight is but it’s like a magic bullet for me. The H buffers are a cheaper process.

When you go to range take lowers with buffers you want to test and you can swop lowers if you find that easier. Not that buffers are difficult.

PB

8

I am sold on Vltor/BCM A5 buffers. I don’t even know the what their standard weight is but it’s like a magic bullet for me. The H buffers are a cheaper process.

When you go to range take lowers with buffers you want to test and you can swop lowers if you find that easier. Not that buffers are difficult.

PB

9

I run H2 buffers on everything except the SBRs which get an H3. All rifles have been run in the coldest temps with .223 ammo and function without issue.

10

H2 here as well. H3 is just too heavy… too much reciprocating weight. My BCM 14.5 middies work better on H buffers, but they’re freakishly smooth.

11

I tend to run regular H buffers paired with Sprinco Blue springs in most of my 11.5-16” carbine/midlength guns. I’ve tried H2s and the guns ran fine but for some reason I feel like I prefer the recoil impulse with an H vs the greater reciprocating mass of an H2. Given the relatively minor weight difference you wouldn’t think I’d even be able to tell but I felt like I could at least.
I did use an H2/Sprinco White spring during my rather short-lived experiment with a 20” upper on a carbine lower. Ran fine but I just ended up putting a fixed rifle buffer/stock back on it.

12

Throw an H2 in all of em and go in peace.

BCMs are gassed to run. They will literally run anything from a Car to an H6 and everything in between.

13

Our 16" carbine length gas systems run a H2 buffer with Sprinco blue springs. On my 14.5" SOCOM carbine, I use a BCM intermediate RE, a VLTOR A5H2 buffer and a Sprinco green spring. All run great.

NYH1.