Interesting results. I have been using that Remington bullet for a several years for higher velocity 45-70 loads because it is pretty cheap.

Last year I was working up a 45-70 load for my single shot that pushed a Barnes 300gr TSX FB at 2150fps. The plan was to take that one to Africa for plains game but the rifle broke down right before the trip. This year I was playing with the same bullet in a 45x2.6", loaded to 458wm specs it was pushing 2740fps out of my 22" barreled Number 1. It's a flat shooting load, with a 50y zero it only drops 4.5" at 200y. The intended bear hunt hasn't happened yet to test it out though.

If you want to test this bullet let me know and I'll send you some. I still have a bunch that I have not loaded yet.

Edit

The TSX FB is the "spitzer" version of the bullet so its not good for use in tubular magazines.