Can anyone tell me but is the flash hider on a XM-177E2 just a big flash hider on a 10.5" barrel or is it a longer barrel and the flash hider acts as a kind of sleeve over it?

On a true XM177E2 clone, the barrel is 11.5 inches long and the flash suppressor is scrwed onto the end of the barrel. This occured because thew original GI issue piece was also something of a sound suppressor as well as a flash suppressor, so the innards of the thing have a suppressor function.  Civie replicas of couse are just smooth surface, non sound suppression pieces.

The sound suppression function doesn't quiet the thing by any means. It was simply intended to reduce the sound to the same level as a full 20" rifle.

+1 for above info. On both the 10.5 and the 11.5 barrels the flash suppressor or " moderator" was 4.5 in long and was screwed to the end of the barrel.At some point (1970's????) the ATF declared the moderator was a silencer and you need to register them.

UXB,that pic makes me wanna cry.. As bad as knowing what "capt crunch's" job is!!!

Thanks a lot guys.