Yes, small magnum rifle primers can. Remember magnum primers give a little more kick. So you may want to use about 2 grains less powder so as not to overpressure the 5.56. Or start at the lowest range listed, then work up if you have time to try them out at the range. I have thought about using magnum primers for all my regular reloading to cut a little back on powder use to stretch the power for a few more shells.