My Armalite is a 300SAUM and in a gas gun, its pretty hard to beat.
My velocity is very conservative at 2715 with 210 Bergers and its an easy sub moa shooter out to the 1150 yds I've taken it so far.
I've ran it as hot as 2940 but its too hard on brass with the semiauto. In a bolt action with a 26 or 28 inch pipe, 3000 wouldn't surprise me at all.
I'd try the 208, 210 or even 215 hybrids if you decide to build one.
I would take the 7mmSAUM first, but the 300 is better than I ever expected and I'll be using it to hammer some long range speed goats this fall...suppressed of course.
Here was some load checking this past spring.