I am using AA#9, while if you load it at max, the powder is at the base of the bullet, with reduced loadings, like when shooting lead(or trying to enjoy shooting without dealing with that recoil) there is room for setback. The thing to remember with the Sig is with just .015" of setback it raises pressures substantially, give it more and bad things can go bye,bye. It is NOT wise to rely on the powder to keep setback from happening. While careful loading and not repeatedly chambering the same round can also keep concerns down, I just don't care to play that game with that caliber. A 1000 count box of Berry's is cheap enough to not even bother