The 7mm rem ultra mag short has a slightly smaller case than the 7mmwsm so it will produce slightly less velocity.Do not believe the comparison between the 7mmrem mag and 7mmwsm in the browning and winchester adds as browning and winchester have used lies and deception to make the 7mmwsm appear to be superior to the 7mm rem mag.In reality the 7mm rem mag will produce approximately 100 fps or more velocity than the 7mm wsm.