In my father's expirience with his 650, it wasn't the case, but the primer that contributed to the pull back. The old Win nickle plated primers would pull back and the new unplated ones wouldn't. I swapped him for some of the newer ones and along with the dressing of the squared edge of the decaping pin, the problem went away. Ii think your Speer cases would be good to go.
Drugs are bad because if you do drugs you're a hippie and hippies suck.
"If you kill enough of them, they stop fighting."-General Curtis E. LeMay