One thing I learned over the years is Copper or brass when worked (stretched,squashed,stomped on,whatever) gets hard........ your (MY) best trick is to anneal it(soften it) is put it on a hot stove burner it will change colors QUICKLY so be ready when it is turns light to medium Blue grab that piece of wire that you already have put thru bolt hole and throw it immediately into cold water,now you have a nice soft copper gasket that you can use over and over Used to do it w/cartridge cases when reloading ......Watch Carefully(color)-- Move Fast