I can vouch for that; @18bravo had access to weapons and equipment that are not standard issue to regular forces. Mainly because of the unique mision requirements that people like @18bravo have to undergo.
That baing said. A general-issue M4 that a tanker would have would look like this.
Standard Colt (or FN) M4A1 Carbine with a 14.5" barrel, fitted with an Aimpoint CompM4 an AN/PEQ-15 laser pointer and some sort of white light illuminator. If earlier in the war, a CompM2 (M68 CCO) and an AN/PEQ-2A IR laser pointer.
SF-types would have the same setup, but with much shorter barrel lengths, to enable them to traverse through confined spaces; though most times, they would also have 14.5" barreled carbines as well… Again, mission requirements would dictate equipment choices.