Hi, what brand of primer is he using? Some are more "soft" than others and may tend to puncture more (Cheddites for one). Also the length of the firing pins can cause this. A case in point is my 16ga D. Gotobed 16b hammergun. When I first got her, almost every primer was pierced, I was using RST's (which use Cheddite primers)and solved the problem by having the strikers shortened up some and the headspace adjusted. Some guns will pierce primers more than others, just depends. As to being dangerous, not all that much to worry about. The problem will be firing pin erosion from the primers if they are not cleaned.
Hoped this helped some.
Good Luck!
Greg
