You probably already know this, but I suggest you use magnum primers with reduced loads suggested here. My first try I used 225 gr Hornady SP/ about 36 grs H4227 and standard primers and got several hangfires. They make me really nervous so I stopped shooting them and dismantled the rest. Went to magnum primers and the problem went away.
My very favorite reduced load in .375 H&H is 38.7 grs SR4759 under a 200 gr Sierra FP for 2300 fps. That's all you need for a deer load in this caliber. Very accurate too.
Good shooting!
