.338-378 Reloading help please

[tdunc300ultra]

Hey - This is my first post so please stay with me. I have a .338-378 that is bone stock that Im having a heck of a time getting to shoot anything. The main purpose for the rifle was to shoot longrange. I have several other rifles that Ive had built, but Id like to try and keep this one stock if at all possible, if possible. Ive tried a ton of bullet and powder combinations with very little success. Ive been trying between a 225 grn bullets and 250grn. Any help or pointers would be great, thanks - Ty