I took the Mark X action and a barrel chambered for 300 Wby to the gunsmith to be seated. The gunsmith is just starting out and doesn't have a lot of equipment. He said he didn't have go/no go gauges for the 300 Wby yet so would need to either rent/buy a set in order to install the barrel. I have read that what's needed to install virtually any of the belted magnums are the same gauge- headspacing on the belt. Is this correct that he can use a set of "belt" gauges rather than full cartridge ones?