And why not? If you have bullets jumping crimp, you can be inadvertently adding airspace to the case. That is solved by proper case prep and bullet alloy and fit.
I have experienced the same with AA#9, and only using soft alloys exactly what lloyd says not to do in post #35. Use a hard alloy, lots of driving band (IMO this is a requirement), or add a gas check and the problem goes away. That lends further credence to the idea it's recoil based, specifically jumping crimp.
Fix that, and maybe primer choice will become the primer mover.
I guess most people would fix that by crimping the heck out of the round, but I don't like that solution when we have antimony, gas checks, M-dies, and great bullet designs in 45 cal at our disposal.