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I find that very old Sav 99 rifles are good for 80 kpsi with 6mmBR brass, but stretch the brass ~ .003"
The 303Sav priv brass is now 50 cents, and the situation is very different when 303Sav brass was very hard to find or fabricate 5 years ago. The 303Sav case base is .439" making it unique.
The 303 Sav brass is very strong like 30-30 brass, but unlike the 30-30 there are no wimpy actions like the 1894 Winchester or Marlin 336 that are chambered for 303Sav. Still I hear that the 303 Sav is SAAMI registered at 34,000 c.u.p
I would double that pressure for optimizing my performance.
I have a Sav99 303Sav, and I have done what one is not supposed to do, shoot 30-30 ammo in it.
This is bad idea because the base dia of the 30-30 brass is .4195".
80kpsi with that combination could be a real mess, with gas ruining parts of the rifle and maybe parts of the shooter.
I would use 150 gr Nosler balistic tip and Varget