Ed,
We discussed primers being spit out of Cheddite hulls used in autos on this thread. Not as much of a concern on doubles.
http://parkerguns.org/forums/showthread.php?t=23282
Three solutions:
Different primer.
Primer Pocket Peener (formerly William's product, now BPI has them)
If shells are already made, cheap dollar store fingernail polish around primer after already seated if you fear they will come out. It works and waterproofs. Clear or colors. I used blue for steel loads, red for non-toxic when I reload waterfowl loads.
Threaded Mode