New Army "Caliber Configuration Study"

[cory]

Hornady's 9th Ed. reloading manual has .338 LM at an ~MV of 2800fps at max pressure with a 250gr BTHP (B.C. 0.670) out of a 24.5" barrel.

Barret lists 50 BMG at a ~MV of 2750fps with a 29" barrel and 2500fps with a 20" barrel, both with a 661gr (what looks to be a BTHP) (B.C. 0.62). So for comparison to the .338 LM we could say 2625fps MV for the 50 BMG.
http://www.barrett.net/ammunition/50bmg

I'm not sure how using a .338 Norma Magnum would change the MV.

All that being said, I think it's fair to say the .338 won't be as effective as the .50, but will it be effective enough to meet mission requirements.