Sorry if this is a silly question - I'm still pretty new to bolt guns. I mentioned to my dad (who used to shoot a lot in the '60s & '70s) that I was dry fire practicing when I got the chance and how it seems to be improving my trigger control (groups are shrinking). He said that I might want to use "plastic practice rounds to avoid causing a problem with the firing pin or mechanism getting deformed" or something like that. My understanding is that this is not an issue with modern centerfire rifles. Any thoughts?