I do a lot of 12ga &28ga on a MEC 9000. I would suggest sticking to one type of hull. There are some that you can "interchange" but for just starting out, pick one and learn it. I use AA HS hulls, and have built up quite a collection of them. I seem to get quite a few reloads before the crimp starts cracking out, at which point I make them in to field loads, and toss them (not in the field...I hate that). I use E3, and 20-28 powers, both are VERY clean burning and you can make a good crimp with the loads. I have gone back to the Winchester brand wads, the Claybuster wads seemed to leave lots more plastic residue in the chokes than the Winchester ones did. With a 600 you might need to resize the brass once in a while if you are shooting an auto, or some pumps. I would also suggest going to MEC's web site and downloading the manual, read through it about 3 times before even putting one shell in there. While you are out, pick up a couple free power pamphlets, and they should have a good starting point for the reloads. I do 17 gn of E3 with a WAA12 (white) wad and 1-1/8 oz shot in a AA HS hull. That puts it out there at about 1200 fps, and for "light" loads I do a 16.5 gn of E3, WAA12SL (pink), and 1oz of shot. Both with a Winchester 209 primer. I even have some 7/8 oz shot that work really well, but I don't remember the load exactly so I don't want to post it. Remember to take your time, and be cautious! You?ll get the hang of it soon enough.