old colonel,
I think you should look to the expander button, for your problem with loose bullets.It sounds like it was made for full size 44 bullets. I suggest you remove the expander and try your bullets(deprime by hand,belling not as important with jacketed bullets, but if you try cast, bell some other way). Once you have cases sized to hold your 423 bullets, fire one;then if a 44 bullet easily slides in, it would be ok to use. I suggest you place two targets,side by side, load both barrels and fire the right barrel at the right target; then as soon as you can get on target,fire the left barrel at the left target. Let the barrels cool to ambient temp.between each set of two rounds.Then when you have fired all six rounds, place one target on top of the other and mark it's bullets impact holes. I find this is the best way to tell whether the barrels are crossing or shooting wide.Do your shooting like you described, but hold on with both hands and build up your rest so you sit up straight( and rock back in recoil). This is just my suggestion, after all, it's not my rifle.
Mike
