Several years ago I was in a gun shop in a small desert town. A older man had passed away and he was a dedicated caster and shooter. His kids scooped up all his guns and reloading gear and took it to this gun shop. At that time there was little interest in reloading much less casting. I bought all the man's sizing dies and sizer. I also bought most of his gas checks. I also bought a friends gun collection and casting gear. With it came lots of gas checks of all kinds, Lyman, Hornaday, RCBS, Sierra. I don't think any of them are the same size. To use some of them I have to use a punch to open the gas check enough to go on the base of the bullet. I also found that mold makers have their own idea what constitutes a 30 caliber, at least regarding the base. I even have a beautiful single shot in 225 Winchester. To shoot cast in that caliber requires the dedication of a monk.