This is a 1917 Sav 99 250 Sav take down that I drilled and tapped for scope.
I threaded and chambered a 6mmPPC shilen stainless select match take $50 take off barrel for SAV99 and 6mmBR.
I have been shooting it at ~ 80,000 psi with the same case head as the 308, but the 308 case head cannot go that high. The primer would fall out. The 6mmBR limit is a pierced primer. I use the toughest primer, the CCI 450 small rifle magnum primer. I run it just below the threshold of a pierced primer.
The brass stretches ~ .003".
The action locks up in the rear.
Different steel with different heat treat of alloy may have different yield strength, but they will all have the same modulus of elasticity. That means it does not matter what vintage Sav99, they will all stretch the brass the same amount.