Originally Posted by Pisgah

I will second the idea of using a hand priming tool. A dozen rounds is enough to give you the "feel" of things as the primer bottoms out. In thousands of rounds loaded, I have never had a single problem that could be blamed on improper primer seating. The "ideal" scenario is primer seated just below the cartridge base with the anvil in full contact with the case and the primer material within just slightly stressed in direct contact with the anvil. I would think that this being too deep for reliable functioning would be a sure sign of a too-short striker or firing pin.