Check your main spring screw and ensure it is tight (located under the grip).

Make sure you are seating the the primers completely, this seems to be a common problem with those just starting to reload this cartridge, compare against factory ammunition will determine if it is your reloads or a gun issue as others have stated.

In my testing WLR (Winchester) primers produce the best results with all but a few powders and those are not commonly used in the US.

good luck and be safe
Ruggy