I have a plate that is supposed to go on a MEC 600 10 gauge so one can load 10 gauge 2 7/8". I think the MEC bases can also be moved up to by way of a second bolt hole in the column making the change more permanent. I will have to look at mine to see if I am remembering correctly.
I've had as much luck loading them on some old tools I've picked up. I have an old decapper and priming tool as well as a 10 gauge collet for my MEC super sizer. I only use the super sizer on hulls that were fired in someone else's gun. If they are new hulls or fired in my gun I don't worry about resizing the base.
I have been loading everything with roll crimps for mine and have had good success with it. It goes pretty quick and once you are set up one can load as quickly as with a MEC 600. It ends up being more like rifle or pistol reloading where you perform one step on each case then move one to the next step rather than loading one round to completion as with a shotshell loader.
Shoot me a PM with your email address and I'll send you an excel spreadsheet of a bunch of 10 gauge 2 7/8" loads. Lots of good information.
Mart
"...I advise the gun. While this gives a moderate exercise to the body, it gives boldness, enterprize, and independance to the mind. Games played with the ball and others of that nature, are too violent for the body and stamp no character on the mind. Let your gun therefore be the constant companion of your walks." Thomas Jefferson