The M60 and M47 "Teams" are made up from the 2 Grunts/Riflemen carrying M16s. In my unit and generally all units worth a 
have all members of the Squad trained in all weapons in the unit.
Cross training is a standard in the US ARMY. And is done by all "effective and efficient " units, in NATO, etc. So if one man it KIA'd/WIA'd another man in the Squad can pick up the weapon and use it effectively.
So yes, with the Driver & TC staying in the Track. You can only dismount 9 of the Squad. And generally in many cases everyone in the Fire Tm ended up carrying a heavy/ier weapon. E.g. M60 or M47, M203 GL or M249 SAW. And depending on the mission some may also be carrying an M72, along with M60 ammo, etc.
If you are carrying the M47[the Tracker and disposable Missile] you will be packing your M16, most likely, too.
The M60 Gunner packed a pistol, the M1911 .45 or M9 9mm Beretta. Based on the date of issue of those pistols. I.e. @ '85 our .45s were replaced by the M9.
So yes you are packing a lot of gear/weapons/ammo. And with Mech units you could carry some extra ammo, M47 rounds, etc. in the Track. Plus a good amount of .50 cal ammo, grenades, etc.
It was not rare to have Fire Tms short 1 or 2 troops. Dismounting only 3 troops. The Fire Tm would end up carrying an M203 GL, M249 SAW and the M60 MG or M47 MAW in many cases. Again, that is another reason for weapons cross training.
When I was a Plt Ldr in the 101, '80-'81. What you had on your back/rucksack when you got out the aircraft, etc. is all you were going to have until/if you got resupplied. But we were trained to use some other counties' weapons too. E.g. AK-47s, etc., etc.
By the time of REFORGER '88 when my M113 Mech Co deployed to that FTX from Ft. Benning, GA. AFAIK all the US Mech Inf units in West Germany had M2s, by '86.
Our Mech Hvy Bde was part of the 18th ABN Corps.