I assume you are reloading these shells? If so, what reloader are you using? I ask because atleast on my MEC 650 and I believe all the newer ones have it but the last crimp station puts an inward taper on the crimp to help feeding of the shell in pump and automatic shotguns. Some older reloaders dont have this feature.
"...and that's the bottom line, because Big Yac said so."