I have been shooting it using CCI #11 Magnum, standard CCI, and even Remington caps and it fires perfect. In fact it fires so fast you would think it is a modern centerfire rifle. I am very pleased with 777. The other nice thing about the stuff is clean up. I take a large plastic glass, and put VERY hot water in it and some dish soap (just a drop or two) then work a patch in the soap water. Pour a quart of boiling water through it afterward, then a hoppies #9 patch or two and some Rem Oil before storing. This stuff really cleans up nice.... I just wish all my rifles liked the stuff. I have two of the four that are being stubborn about the 777. I can not get them to group using the stuff. I go back to the pyrodex and they are dead on the money again.