Cheapest way may just be an old 600 JR. press. I loaded 3" .410 on one many years ago. It was not too bad because it was a low volume need. If I was loading many thousand .410s a year it would be too slow but for a few boxes now and then it worked well.
You need to add height to your loaders column. Take a closer look at your machine. There are two holes in the lower end of the main shaft column, (Mec part #84), and your machine most likely is using the lower of the two. If you move it upward you will gain column height. Might require only this step to alter your machine. But nothing can be that easy right? I bet you also have to drill another hole in the column to move pin #117, (see MEC parts list), half an inch. Then adjust the wad guide and other stations as needed. If the column is not stable in the upward position I would drill and tap a hole in the base of the shaft and add an extension to make it longer and more stable.
If you look at the MEC Sizemaster owners manual they show this is how they change from shorter to longer shells. Go to the MEC site and look at the pdf page 11 and they have a clear photo of what I am talking about.
Last edited by KY Jon; 12/12/15 11:39 PM. Reason: Added last part of message.
