I have a T/C Black Diamond XR and both the 250 & 300 shoot well out of the rifle. I found that 110-120 grains of powder seems to give the best accuracy.

As for which one you should shoot I would suggest you get a package of each and work loads up to see which one gives you the best group. If all the ranges you were going to shoot were 100 yards and under I would go for the 300 grain only because of the larger size.

If your shots might stretch out to 150 yards or further, then the 250 grain will give you the best long range flight of the two although from experience I will say that the 300 grain is no slouch at long range.

Another projectile you might want to try out of your rifle is the Buffalo Bullet Sabot SSB in 375 grain. I buy them at Cabela's. If your shots are 100 yards and under this would be a fantastic hunting bullet. The down range energy is fantastic. With the hollow spitzer point the expansion in my tests on water soaked paper were very impressive to say the least. I had excellent results shooting them with 100 grains of Goex....