Well it turns out that I have access to a reamer for the 450 3 1/4 so it seems like the logical choice to go that way. I guess the thing that I hadn't considered is that with very limited load data to work from I basically have no load to regulate new rifle too. I now realize to be successful I would need to build a single to develop a load of my satisfaction and then move on to the double. Too much for me at this stage of the game I think.

Now about the action. I would like some opinions on hammered vs boxlock. I have been thinking about the hammerguns as at one point we hunted grizzlies on horseback so a rifle in scabbard could be left loaded but uncocked. I realize we may never get the grizzly hunt back in Alberta but one can hope.