I just bought a nice looking Rolling Block in 7mm. The gun shop I bought it from told me it was a strong action and it was good to go, and they sold me a box of Winchester Super-X 7x57 Mauser to go with the rifle. While doing research online to find out what model I had, I came across info which said the 7mm is not safe in this gun, due to excessive headspace issues caused by the 7mm cartridge being a bit longer at the turn of the 20th Century than it is today. I also read that today's 7mm Mauser factory ammo is too hot for the action, regardless of headspacing.
I also bought George Layman's book, which was very helpful in identifying my rifle as a Model 1902.
I bought some Plasti-Gauge and measured about 4.5 to 5 thousandths headspace between the case head and the rolling block face, with the block closed and the hammer down. I'm told max allowable here is 0.003".
I thought this round headspaced on the shoulder, and so I thought perhaps I could decrease headspace by moving the shoulder forward a bit, so I took a 30-06 case and ran it through my 7mm die. I ended up with a weird looking, very long neck 7mm case with the shoulder moved forward about 1/16". However, the case was about 1/4" too long to go into the chamber, so it's apparently headspacing on the case mouth, rather than the shoulder, as I'd thought it did. I haven't yet tried trimming the case neck back to get the headspace I am seeking. Perhaps some more tinkering/experimenting there...... Does anyone know for sure where this round headspaces?
In George Layman's book, he unfortunately didn't go into much detail about it or the alternatives, but he explicitly made a highlighted point of saying the 7mm rifles should not be shot at all (page 31). So, while it seems like a nice rifle in great original shape, I am thinking perhaps I should take it back to the gunshop for a refund. I guess the only other option would be to send it out for rechambering/reboring in a rimmed caliber. Your thoughts on that? The rimmed calibers don't have the headspace issue? I'm looking at a couple older ones in 43 Spanish now.