XM177E2 Review with Griffin XM Linear Comp

[GRIFFIN ARMAMENT]

There is no baffling internally and it was not designed to reduce sound but to reduce muzzle movement and rise inside the aesthetic and external dimensional envelope of the original device. It's a linear compensator. The original device had a monolithic baffle with 3-4 baffles and had coaxial chambers and porting and was designed to reduce sound and flash. The vents I think you are referring to are the slots in the flash suppressor which was added in front of the moderator, which began life as a minorly functional mini sound suppressor on the Colt 607 carbine- a shortened telescoping A1 stock 10" carbine with cut down triangular handguards that I believe was fielded to dog handlers. That moderator had an ~.25" bore, and that was found to destabilize bullets, so the XM177 moderator not only added the flash suppressor to the moderator, it also punched the bore to .295".

I think the reasons the moderator existed were probably flash reduction and the Army wanting the carbine to be no more dangerous to operator hearing than the 20" A1. So the moderators dropped sound ~3-5DB's and reduced huge fireballs to a level more like we're familiar with on the 14.5" M4 carbine with A2.

The M4 carbine barrel was Colts answer to the NFA determination on the moderator- the military still wanted the M203 grenade launcher ready carbine with the ~15" barrel system length, and Colt didn't want the extra paperwork and export issues for foreign government sales.

The real XM moderator weighs 10.5 ounces - and that combined with the aluminum stock gives the XM177E2 a feel almost like a Thompson machine gun- it has a confident heft to it. When I picked up an XM177E2, at first I thought the barrel was heavy under the handguards.