I started at 48.0 grains and quit at 50.0 because my accuracy was nice and velocity was what I wanted.
Brian Pearce did an article in Handloader a few years back on loading the 45/70 and my velocities followed his with H 322. It's my favorite powder for heavy loads.
I used R -P brass, CCI 200 primers and applied a heavy crimp with the Lee Factory Crimp Die.
Good luck with it!
I have some old test data showing nearly 100fps variation by simply adjusting the FCD crimp - using H322. This is something I did in 2002 when I was first looking for a load for the guide gun. This crimp sensitivity always perplexed me and made me wonder about the suitability of the powder for this application.
I ran H322 up to 52gr pushing a 405gr Remington JSP. The 50gr target had the best group, but it wasn't a "one-hole"-type load. I had an H4198 load that was a real one-holer. As you know, the Guide Gun has sweet spots, and I never found one with H322.
I guess I'll load up some 49.5gr, 50.0gr & 50.5gr to see if there's a zone I've missed. I don't think the powder is fast enough to warrant finer increments - but maybe I'm wrong.
