Well, the figures I quoted are "straight from the horse's mouth", in that they came from the people who make Power Belt bullets. However, whether these figures are what you will actually get from your particular gun can only be determined by shooting it at the various distances involved!! My rifles don't give as high a muzzle velocity with 100 grains of Pyrodex and the 295-grain bullet, so my trajectories are not as flat.

Keep yore powder dry!!