Idaho, in general you're going to have problems getting long cases to chamber for ANY longer-than-standard case. You have to size down the top 1/4 to 1/3 of the case so it will fit into the throat of the chambers. So for my .45 Colt shells, I use a .44 sizing die to squeeze them down to fit. For the .445 Supermag shotshells I made yesterday for use in my 44's, I used a .40/10mm sizing die to squeeze them down. This might also work for the .414 Supermag cases as well.
