The old standards of 68 to 70gr. of IMR4064 ( or equivalent) is an elk, moose or other game buster and needs no speeding up. This is with 270gr. bullets. With 300's, 64 to 65gr. works just fine.
: Most .375's will hold these bullets into less than 1" at 100yds. and recoil is soft, as it should be from such a magnificent round.
: I've shot a few 250gr. Sierra BT's (when fireforming) and while very accurate in my .375, they are a very soft bullet, suitable for deer only perhaps. I'd not shoot a moose with one, unless traveling no faster than about 2,400fps. There are much superior bullets available.
: The 300's run around 2,450fps and the 270's in the 2,650fps to 2,700fps range, depending on the rifle.
: My old buddy, Lester J. Hawkes had a large jar full of perfectly expanded 270gr. Power Points recoverd from Montana Elk and B.C. Moose using a mere 68gr. 4064 from his 1951 M70, .375. My BRNO, 602, in 1974 put his old loaded ammo into 3/4" yet it had been loaded for almost 12 years.
: It's the bullet and placement that kills the game. The bullet has to perform properly, and with normal lead-core bullets, veloctiy can hinder rather than help.