OK. I've been loading for mine now for 2+ years, using the same RA brass from the early 60s. Once I put the port buffer on it, the brass shows very little damage from firing. There are flute marks on the brass, true enough, but after tumbling, you can hardly see them. Since the mechanism of the rifle depends on a case suspended inside the chamber on high pressure gas, I don't worry about reusing the cases in the PTR91. I do not know whether the presence of the flute marks on the brass would adversely affect its performance in a bolt rifle or not, but I doubt that it would.
Without the port buffer, the brass takes a beating on the scope mount and on the rear of the ejection port.
I don't immediately recollect my H4895 load, which the rifle likes best, but using a good 168 grain match bullet, CCI standard large rifle primers, and the aforementioned RA military brass, 43 grains of Varget makes a great middling load that is more accurate than I can shoot the rifle. No pressure signs.
Even better, since I got one of the early "tight chamber" rifles which are cursed by many, but which I love since I handload for it anyways, I get ZERO case stretching, and the force required to resize this brass in a RCBS standard base, X-die, is virtually imperceptible. I can reload the same case and fire it repeatedly with no stretching, using the moderate load I offered above.
YMMV.