Lumpy, welcome aboard, and Happy New Year.Yes get the Mec, Mark 600 Jr. To load 2 1/2" shells you will need a 1/4" spacer. You can buy them for about $16.00 through Mec. I made mine from a piece of 1/4" aluminum that starts at the 3rd station, putting powder, wad and shot in and goes around to the crimping stage. If you are going to roll crimp, which makes a nice shell, you will need to get that also, $29.00. You could also 6 crimp, and if you do, there is a brass starter crimp made that starts the crimp excellent, but really only for new uncrimped shells, that is about $15.00. You can buy this through Ballistics Products.
As someone mentioned below, if you are going to roll crimp you will need the clamp to hold the shells, simple jig if you have the special clamp. That cost about $30-$40.00 depending on where you go.
I didn't like the plastic wad fingers that came with the Mec, but I got used to it. With the Mark 600 Jr. it is really impossible to forget where you left off because of the way a bar is set up on the powder and shot bar.
The 16 ga. Reloaders has quite a few 2 1/2" reloads most all are under 8,000 psi.
Don't be afraid to ask for some reloads, those from the 16 ga. Reloaders have all been tested by their ballistics expert.
Also like Drew said, email us and I will give you the bushing numbers for the different loads. Most were using Cheddite shells with their primers, which are Cheddite 209, identical to Winchester 209 in performance, and either Unique powder or Longshot,that will give you 9 different "receipes" from 1094 fps to 1204 fps, and psi from 4333 to 7860.