Just a bit of an update.
I loaded with 80gr. of H4350 - that looked to fill the case roughly to the bottom of a 450gr. Hawk bullet.
I (still) don't have a chronograph so can't even guess at velocities but accuracy shooting offhand is quite acceptable in hunting terms and nice round holes. Easily ploughed through 16 inches or so of dry pine boards and well into the log they were up against. That with the soft Hawks. I can see that a good heavier solid would give good penetration.
This was one of those gatherings where everyone gets a chance to touch off a round or two so no grouping work was undertaken, just a load of fun!