BCM 11.5" KMR SBR upper question

[TehLlama]

IIRC, I believe Crane initially went with the 10.3" is because that's where the barrel profile changes in relation to the grenade launcher. They were also more size oriented as SOCOM needed the rifle to be able to go through bulk heads sideways.
I have a 11.5" BCM KMR and it has run like a top with an H2 buffer both suppressed and unsuppressed.

I know they've used 12.5" (and even requisitioned the GL/SSC RIS-II for those) for specific used with the 9" M203 (and M320) setups, but I think the 10.3" was settled on by being the shortest possible CQBR upper setup with an FSP, and for VBSS/suppressed/low-vis stuff the 10.X" setups are really a great answer. Feed them full power 5.56 ammunition and they'll run, and that's about the smallest form factor for a 5.56x45mm upper that can really work well. The 11.5" was a pre-existing setup that once revisited conceptually makes a ton more sense especially as a base for a .civ weapon system. 12.5" still works pretty well as a suppressed rifle base, and arguably an ideal urban recce - do-all carbine setup depending on optics/can/accessory setup.

[GrahamKAC]

I've got a DD 10.3 barrel setup with a 9" KMR. Great setup and I was able to notice a slight reduction in weight when switching from the 9" DD MFR to the KMR. I run mine suppressed 100% now that I've got my suppressor. With that said there is a noticeable recoil impulse that I'm not quite happy with. Even the most basic of users familiar with the AR platform can tell that thing is severely overgassed. I'm currently using a Spike T2 and have got an H3 on the way. Still considering the BCM 11.5 as they are known to be soft shooting for the size.

[domestique]

I've got a DD 10.3 barrel setup with a 9" KMR. Great setup and I was able to notice a slight reduction in weight when switching from the 9" DD MFR to the KMR. I run mine suppressed 100% now that I've got my suppressor. With that said there is a noticeable recoil impulse that I'm not quite happy with. Even the most basic of users familiar with the AR platform can tell that thing is severely overgassed. I'm currently using a Spike T2 and have got an H3 on the way. Still considering the BCM 11.5 as they are known to be soft shooting for the size.

Maybe try an adjustable gas block like a micro MOA would help. I'm debating about trying one on my 11.5" KMR setup once my 556-RC gets out of jail.

[GrahamKAC]

Trying to avoid an adjustable gas block of at all possible. I like to run everything from cheap wolf to mk262. Unfortunately I don't think I've ever seen a micro MOA adjustable in stock.

[Iraqgunz]

The issue is the gas port size. Your current one is probably about 13% percent larger than BCM or SIONICS.

Trying to avoid an adjustable gas block of at all possible. I like to run everything from cheap wolf to mk262. Unfortunately I don't think I've ever seen a micro MOA adjustable in stock.

[GrahamKAC]

The issue is the gas port size. Your current one is probably about 13% percent larger than BCM or SIONICS.

I'd agree. Unfortunately I didn't do as much research when building this gun, as it was my first SBR. I've since learned that these guns are almost notoriously over-gassed.

I'm still up in the air in regards to selling the 10.3" DD barrel and 9" KMR, and replacing with a 11.5" BCM lightweight and 10" KMR.

I haven't gotten a chance to shoot an 11.5" in person though.

I intend to run mine suppressed 100% of the time.

[kaltesherz]

I've got a 11.5 BCM KMR that I run 100% suppressed with an LMT Enhanced Carrier and Vltor A5 and couldn't be happier. The only thing I'm changing is the can, otherwise the set up is pretty ideal for my needs.

[cop1211]

Sweet paint job.

[the 556 guy]

I've got a 11.5 BCM KMR that I run 100% suppressed with an LMT Enhanced Carrier and Vltor A5 and couldn't be happier. The only thing I'm changing is the can, otherwise the set up is pretty ideal for my needs.

Which can is that, and why are you changing it?

[Willysjeep]

To the OP. For my first I went 11.5 BCM with 10" KMR to get the extra dwell time. Then put on a SLR sentry 7 gas block to tune it for best unsuppressed and suppressed settings. With an H2 buffer it's smooth.