Originally Posted by
Alaska3006
MK18 type 1: NSWC assembled carbine with contracted and /or overhauled parts complete with all accessories to current standards at time of build will work with H or H2 and could have shipped with either. Units will balance buffer to ammo requirements:
H okay with M193/M855. (all ship board MK 18’s should have H buffers as this was the standard at the time of assembly).
H2 needed for MK 262/ R2LP & will run M193/M855.
H3 may be needed for an extreme cases or when the gas port is eroded but the barrel still groups.