Sometimes guns are hard to open because the firing pins stick into the dents they have made in the primers when fired. Drag marks on the shells often show that the pins stuck.
I gather you are not seeing such marks, and that the shells are hard to pull out of the chambers after firing.
Shells with steel instead of brass sometimes stick in otherwise OK guns. Especially, if they have been reloaded; the steel seems to spring back from resizing, leaving it oversize, so the next firing expands it too much for extraction.
