Though not at the longer ranges you were shooting at, I have some experience from shooting IHMSA matches with similar Unique loads in my .41 and .44 Magnums. They did quite well. 1000 FPS with any .41-.44 cal. 220-250gr Keith bullet is nothing to take lightly. It was always fun to watch the reactions of others when they would see my "light loads" topple the rams. A good hit never failed. I did just as well with Unique as I did with 2400, all things considered.

I am not saying I would shoot at a game animal with such loads, especially at any distance, but as you say, it is surprising what they will do - and you can indeed shoot them "all day" without beating yourself senseless.