Indeed. I think the conservative nature of Army procurement might still see .30-06 prevail, but I would vote for the .276. It actually makes the BAR more sensible, full-auto-ish, Mg-ish, potent round, the partner to this new "lightweight". It lets the Army dither on about replacing the M1919 with a true GPMG the infantry can carry. As wiking points out, the .276 Garand might sideline the M1 Carbine, thus the Army has .45 M1911/Thompson, .276 Rifle/Carbine, and .30-06 BAR/MG. Not logistically far from OTL. I will not predict a SAW at this point but things like the Johnson LMG might get a better look at, the .276 might spur development of a better BAR weapon for the Squad. Of course that seems to suggest the 6mm arguments here argue for .276, rather than a new round as such. Would the USMC persist with the 1903? It occurs to me they might not prefer this new rifle or its round.