i'm partial to the M60E3 - lot of good experiences using one back in the day. it's an excellent light-weight "raider" platform with trucks, armored vehicles, brown water stuff, or doing air assault with. the E4 being a marginal improvement for more open areas, but other than stealing a top cover for the rail, i never really used an issued one. the M60B was a weird one to use on a pintle (dismounted from old Huey's). i think the Coasties have a bunch now, as well as the USFS has a few too for mountain drug field area control.