Never had a primer go off or misfire in 48 years of reloading. I handled them 1 @a time in by old CH press and in my original Ideal Tong Tool loading 30-30's. When I had a doubt about a primer I just put the case into my gun and pulled the trigger. Later on I used, and still use, the Lee Decapping tool. I press the primer back in on my old CH press. The seating stud has a barely visible concave shape so touches primer around the edge. A seated primer is sensitized. When I use the Lee decapping die, the stud end contacts the inside surface of the anvil. Gentle pressure pushes the primer out. I then reuse the primer. As an experiment, I put on a face protection mask and gloves and reseated a number of primers I had removed. I went from light pressue to slamming them in and so far have not had one go off in the process. When fired at the range, never had an FTF. Various primers may have softer or harder metal.
The hammer cuases the firing pin to hit the primer with much greater force than you can on the bench. However DO NOT USE A PUNCH unless you want to risk a finger blown apart.
Today in modern primer manufacturing, a paper or foil disk is placed between the anvil and the explosive mixture. It protects the mixture. Concern about contamination should be minimal. LOL
Frankie B.