475 guy
My only personal big bore pushes a.475" dia. 400gr wheel weight at 1500+ FPS and has a special 5 shot rotary magazine, so I can't speak with experience about working up any loads with any .375. I do think the 375 H&H is personal favorite of hunters around the world and rightly so.

But...speaking purely from other peoples research here...

375 H&H case holds about 96 grains of water and pushes a 270 gr @ 2700fps and 300gr @ 2600fps

375/338 (375Taylor) case holds around 88 grains of water and pushes a 270gr@2700+fps and 300gr@2600fps

9.3x64(a round most people that have posted here seem to think is very real, me included) case holds 87grains of water and pushes a 270grain @2700++fps

416Taylor case holds 93.6 grains of water and pushes a 400gr @ 2400fps

416Rigby case holds 132.5 grains of water and pushes a 400gr @ 2400fps

I know somebody's gonna show up here on this thread and tell us about his personal cement truck that has been modified to fill his Weatherby cases with volumes of powder so colossal that he measures it yards.

Seriously, I am only relaying info here that others tested, but it just seems like a few good rounds never made it into that "factory" box of ammo. I did find some info about these wildcats at 416 Taylor Page

I've got a few 09 Mausers just laying around and allways toyed with the idea of building a 375 and 416 Taylor. After finding this message board I'm starting to take interest in the 9.3 rounds that others here have recommended. Maybe I need another action.

gunmaker
http://users.elknet.net/chico