I've been contemplating a 7tcu or 7-30 waters (in a pistol barrel - 14") also. In my studies - according to my Nosler manual the 7tcu actually has more velocity for the same weight bullets......maybe in a rifle barrel the larger powder volume will have a chance to burn, but in a 14" barrel the 7tcu seems to be better. - At least according to that manual, my other manuals all have the 7tcu from a 10" barrel and in those it gives up about 150 to 200 fps to the longer barreled waters.