Welcome to the true cognoscenti, Bob!

Can you tell us whether the proof-marks on the barrel flats of your.333 specify a 250-grain or a 300-grain bullet? There is a belief that all guns were marked "300 gr max", even though some (most, perhaps?) are believed to be regulated for the 250gr bullet. I'm not sure this is true, and would love to hear of one marked "250 gr max".

The only one I have played with showed "300 gr max" and shot that bullet weight to the sights. I would have bought that gun if the bores were better, they were unfortunately quite dark and corrugated in the rifling grooves and it wouldn't hold any better than about 5 inches. A great pity as it was very fine externally.

Good luck with your load development, you will soon be an expert at neck-annealing at the very least!