I' gonna say the spring in your pistol also or a dirty cruded up fireing pin hole. You said, what, 9 out of 10 fired and the other fired the second time. A bad primer would not fire the second time. I doubt it's the case either. While the case might swell at the head with to hot loads, the primer pocket won't deepen itself. What would happen is the pocket would get loose. Long befor that happen's you'll probably experience split necks unless you anneal. Necks will get brittle from expanding the mouth a bit much the get the bullet started. If we go back to the hot load idea, unless you've been sticking the cylinder, you probably don't have that either. For what it's worth, I'm using factory primer's on some military cases made in 1949 and they work fine!
Weak spring or cruded up fireing pin hole!