I'm going to guess and say the difference is going to be the bullet itself. One may be hollow point and the other may be round nose. You didn't say if they were different manufacturers as well.seif5034 said:what is the difference? I was looking on cheaperthandirt.com at some ammo and they had some 40grain wildcat and 40grain high velocity. So, it was the same bullet weight, the same listed velocity of 1255fps.