At 300 pounds, I'd assume it's doing well. Did you hit the bones?
Also when you butchered, was there many copper or lead fragments to clean up?
Most of the 9.3s have muzzle velocities of 2450 and less with 286 grain bullets, and impact velocities are going to be lower the farther away the game animal is. At lower speeds the fragmenting effect is usually going to be less but not all bullets are made equal.
For example, the Speer 270 grain bullets are very very poor. Super accurate, but I have now killed 12 deer and antelope with them and the failures are impossible to miss. Hits have been from 25 yards out to 375 yards.
Here is the worst one of them all. This is all that was left of one when I hit a very small whitetail buck in the spine (shooting down a steep hill at about 60 yards) and the bullet would was less then 5
inches deep.
Speer advertises this bullet as suitable for large and dangerous game.
I think such an advertisement is criminal. This is the kind of bullet that
causes horror stories against dangerous animals.
I am hoping PPU is doing a lot better job with their 9.3MM Bullet