I eliminated this foreseeable problem by using barrel nuts. My Forster gauges make a pretty tight chamber. I am able to set the dimensions on headspace where I want it. No monkey circus blame game between manufacturers.Shane Lindsey - my concern with a shouldered prefit is after torquing it to spec then having it fail the go/no-go gauge test what's next - take it to a gunsmith? With your shouldered prefit build, which action were you using?