11.5 SBR Buffer & Spring Combo

[matemike]

My 11.5 bcm worked through many range and ranch trips and a couple classes with a standard spring and H buffer both suppressed (M4 2000) and unsuppressed. After, I dunno, 3k rounds, I had a few failure to hold open on last round and after ~4k started having failure to feed when suppressed. I figured it was overgassed. Put in a H2 and new carbine spring from BCM and it's been running good again. I'm sure I'll be due for a tube and bolt springs, which I have on hand, plus a few more carbine springs. They are cheap backup parts.

[Leonidas24]

I own a BCM 11.5” I plan on shooting this suppressed the majority of the time. I want the gun to function both suppressed and unsuppressed. I was looking for the best combo of spring and buffet. From what I read it seems the sprinco blue and H2 is what I’m looking for.

I also planned on using an LMT EBCG with standard bolt to help tame a little of the gas to the face. Has anyone tried this combo? Any suggestions are welcome.

Thanks

If the reported numbers are correct for 2021, BCM's 11.5's are hogged out like no one's business. Gas ports reportedly range from .073-.076. A BRT gas tube to reduce the port size to an equivalence of .067-.069 would be most ideal, along with a mil-spec H2 buffer and carbine spring will run reliably unsuppressed and suppressed. Even lower pressured ammo like PMC should cycle with this setup.

[Alex V]

I’m running the Geissele Super42 spring with H3 buffer in my BCM 11.5. Runs underpowered Russian Wolf/Tula fine with a DeadAir Samdman S and without.

[gaijin]

I got a brt tube and run a sprinco blue and h2. (Bcm 11.5).

Same, no can.

[Leaveammoforme]

Here's the secret combo to cycle everything from light .223 to full 5.56, whether suppressed or not, in a BCM 11.5";

H buffer
M4 recoil spring
Decent mags

[Warp]

vltor a5

I’d do what Clint recommended.

I think BCM’s 11.5s are way overgassed without a can.

They are. BCM earned their reliability reputation by overgassing everything so "it will eat anything"

BRT gas tube sets them straight...IMO my short BCM upper with a can was unshootable until I changed gas tubes

[Steve-0-]

vltor a5



They are. BCM earned their reliability reputation by overgassing everything so "it will eat anything"

BRT gas tube sets them straight...IMO my short BCM upper with a can was unshootable until I changed gas tubes

This ^^ Also an A5 setup with an A5H3 buffer wouldnt hurt. Ive shot a lot of 076 11.5's suppressed and its not fun.

[Gatorgrizz27]

I have an 11.5” Sionics ERGP barrel (0.062” ish IIRC), with an A5H2 buffer and Springco green spring. It runs Winchester and Federal .223 ammo fine, and will lock back on an open mag without the suppressor, but you can feel that it is sluggish. With a Sandman S on, it is very smooth and enjoyable to shoot.

[Circle_10]

I’ve got an H2 and a Sprinco Blue buffer spring in my SBR with an 11.5” BCM upper (purchased in 2020). Even with that combo the recoil is a bit spicy by 5.56 AR standards and it’s ejecting at about 1 o’clock, and I get periodic failures to lock open which I’m assuming must be the BCG outrunning the mag follower, because it sure as hell ain’t undergassed. I previously used a BRT EZ Tune gas tube on another ridiculously overgassed 11.5” in the past and it worked well but I think I was trying to get away with the “band aid” approach this time. Probably ought to just get another EZ Tune.

[17K]

vltor a5



They are. BCM earned their reliability reputation by overgassing everything so "it will eat anything"

BRT gas tube sets them straight...IMO my short BCM upper with a can was unshootable until I changed gas tubes

They bought their reliability reputation with marketing.

They’re earning their overgassed/same shit different day reputation now.