Need some info regarding BCM LW upper

AR/M4 AR General Discussion
1

I searched the forums but can’t find a definitive answer on this: is the gas block in this BCM upperpinned or set screw? And which low profile gas block does it use? Is the BCM LW barrel a .750 or .625 under the gas block? The description on BCM website doesn’t say.

I’m torn between this BCM upper and DD LW upper equipped with their new MFR rail. I know the difference is splitting hairs, though I really want to get the lightest weight possible reliable upper, and is trying to figure out what is the weight difference between these two uppers.

thanks!

2

My guess is you’d get a quicker answer by emailing BCM… they’re usually pretty good about getting back to people.

3

If it’s the same barrel as this then these are .625 under gas block and barrel is dimpled for a gas block.

4

If the rail is run over the GB, it is NOT pinned (no need).

Barrel is .625 under the GB.

C4

5

Thanks Grant, do you happen to know which gas block it uses?

6

Most likely VLTOR or DD.

C4

7

I’d only worry about it if the gas block was exposed, regardless of how you run your rifle. I opted to leave mine unpinned on my BCM 14.5" barrel. Both of my KAC’s were unpinned as well, though they were pressed on apparently. Never an issue, and they were exposed.

8

Interesting, so we really don’t have to pin the lowpro gb if it’s covered completely by a rail system? I guess some red loctite and enough torque on the set screws is enough.

9

You can, but is really overkill. I typically red loctite the screws and green loctite the GB to the barrel.

C4