The discrepancy in energy and velocity between standard ammo and +P ammo is considerably less in a short barrel. Energy and velocity figures are from barrels that range between 4in to as long as 10in in some cases. The longer the barrel, the bigger the difference between standard and +P. The difference in a three inch barrel can be as little as 30 fps, generally considered insignificant. Manufacturers such as Speer make bullets specifically made for these lower velocity producing barrels and they are labeled SB. These are designed to expand at the lower velocity.