John, you are right as usual, I just need to buy some 7.62 gages.
I was just re-reading some of your earlier posts and found the good article on the difference between .308 Winchester vs. 7.62x51mm NATO that you had provided the link for. http://how-i-did-it.org/762vs308/chamber.html
"If you're read all the way through the admonitions about not using .308 Winchester in a 7.62x51mm chamber, then you know that 7.62 chambers are dangerously long compared to what's allowed for .308 Winchester. Interestingly, the cartridge dimensions themselves for 7.62x51mm are identical to .308 Winchester. All that extra space is just to improve reliability of feeding and prevent headspace issues in firearms that love to slam the case into the chamber with enormous force; e.g. machineguns."
"7.62x51mm chambers get away with being so loose because 7.62 ammo is made thicker at the base than .308. The extra brass provides enough material to prevent ruptures, and is the reason why most reloading manuals advise downloading by about 10% when using military brass. Conversely, thinner .308 brass provides more case room, but less leeway in chamber dimensions."
I use only Military 7.62 Brass. Last time, I gaged all my cases with the Dillon 308 case gage at the minimum headspace. In the future, If I go to the Max Head Space in the 308 Gage, then I should be good for 7.62? After I check my barrel and bolt combos again with some 7.62 Head Space Gages, I need to test a 7.62 NATO Go, No Go Gages in my Dillon 308 case gage so that I know how to set my case sizing die.
For my MG 42, I have four West German 7.62 barrels and five 8MM Barrels (3 German WW2, and 2 M53) and four M53 Bolts. They are not all the same, I have numbered the barrels and have an index card with the different barrel bolt combos. I have one barrel bolt combo, that will not lock up on factory 7.62. When I get the gages, I am going to recheck the combos of barrel and bolts and verify my index cards.
I will re-read the link on testing headspace. Do you have any additional advice on how the rollers should feel when testing?