Also, I would only use a firing pin with a vented WWII type, the WWI types can cause destruction of a breechblock when a primer is blown and overpressure gases go back through the firing pin hole. This pushes the firing pin guide back through the end of the breechblock and shears off the small amount of metal from the breechblock that holds the guide. I have replaced several breechblocks that were damaged in this way. Tom Heller sells them.