Daryl,
when Trailboss was first seen in Australia, the first cartridge I tried it in was a 45-70, and was disappointed at the lack of velocity I was getting.
I kept trying it in other big bores, Thankfully I did, because I'm now a convert to it, seems to work well in everything I've tried it in, even a 500 Jeffery, shot excellent groups, and does shoot nicely in every calibre I've tried it in. I use it in my wifes 257 Roberts with a little 80 grn cast bullet.
the other thing I like is that the cases come out clean, no more sooty cases (higher pressure?)
It's really good if you are happy with the 1400-1600 fps range, which for me and what I want to do with cast bullets is perfectly OK.

Regards,
David.