+1 on Ballistic Products manual. Loading larger shot is addictive, whole new world opens up, Super hard #4 buck, F Buck, T Shot, BB's, etc.
You will find that every shot gun you shoot is different and fickle in what they like.
Ballistic produces wads for large shot columns, invest in some.
One of my favorite loads is with the 2 3/4" Active hull or the green Rem 3" hull, 32#4 Buck+13 BB's, 36.0g of Blue Dot, BP12 wad, BGS, 2 slits in the wad 2/3 of the way down, I put BB's on the bottom, then stack the #4 Buck, 4 to a row and put a BB in the middle, then add buffer. This load patterns extremely tight at 40 yards with a velocity of 1275 fps. If you bump the load to 38.0g of Blue Dot, the velocity will be over 1300 fps, and you will loose a little pattern density.
I have been loading large shot since the days of goose hunting with lead shot...no doubt it is a labor of love. The hastle of finding 3" hulls, cost of loading components, etc, and don't forget that many, many load recipes do not pattern worth a flip. You will no doubt need a Mec 12 ga Sizemaster loader due to the fact that it will load 3" and 2 3/4" hulls. Your fisrt order to Ballistics Products will no doubt be in the range of a couple Hundred dollars to get you started, Wads, shot, loading manual, primers, powder, buffer.
The Buffered #4 Buck shot from Federal, Winchester, and Remington are fantastic loads in the shotguns that I have shot them in. It would be prudent for you to take that $250 + the $150 for the Mec Sizemaster that you were going to spend on reloading components and go to the store and buy you a life time supply of #4 Buckshot and be money ahead. Also, go to www.gunbroker and do a search on "Federal BB". Federal is now making a load of 1 7/8 oz of lead BB in a 25 count box that sells for about $25...best money that you ever spent.
Please don't get me wrong, I love to reload my own buckshot, but it is a very expensive proposition to get into and for the guys that think that they are going to save some money, forget that notion.
I think that I outsmarted myself on the hobby of loading Buckshot.