would C-777s be a better investment than more C-17s?

Don’t get me wrong, I think the C-17 (and C-5) is a great plane for what it is, carrying outsized loads into difficult situations.

But how many of the C-17s missions actually need/use such capabilities?

It seems like what they need is a dedicated pallet hauler, like say the 777F, that can
a) carry more pallets
b) carry them farther
c) carry them faster
d) carry them cheaper

If the C-17s and C-5s were relieved of having to haul around pallets and medevac people from Iraq to Texas, there would be more than enough of them to fill the outsized/combat missions. It would also greatly extend their life and preserve them for the truly critical missions.

Number of 463L pallets
————–
C-5 – 36
C-17 – 18
777 – 20 to 40 (more later)

Cruise Speed
————
C-5 – 0.75 Mach(?)
C-17 – 0.74 to 0.77 Mach
777 – 0.84 Mach

Range+Payload
————
C-5 – 2173 nm with 131.6 tons
C-17 – 2400 nm (4445 km) with 80 tons
777 – 4885 nm (9047km) with 103 tons

The range thing is huge because the C-17 is very reliant on aerial refueling. Being able to accomplish many more missions without aerial refueling would free up tankers for other missions and be much, much cheaper.

The pallet count on the 777 is sort of vague because it just comes from looking at the interior view

The given pallets are 96″x125″ while 463L pallets are 88″x108″

The main consideration would be whether to stick with the current floor plan (which limits pallet height to 10′ on the top deck and 5.3′ on the bottom vs 13.5′ on the C-5 and C-17) or to lower the floor to get extra height but eliminate the lower cargo hold.

Of course the floor probably couldn’t get lowered much over the wings so you would essentially have split cargo holds if you went with the lower floor.

Even taking the most superconservative layout of nothing over the wings and allowing some fudge factor there is room for at least 20 full-height pallets