Yeah, they're easy to get, and pretty cheap. I also have a pile of fired 12-gauge cases on hand that I don't use much anymore, which I'd be happy to donate.
You need to use the exact recipe when loading shotshells, instead of varying components like you can with handgun and shotgun loading. This is mostly because the wad has to be matched to the type of case, not only because case capacity can vary considerably but because some case walls are the same diameter all the way up, and some are tapered. If you use a straight-wall wad in a tapered-wall case pressures can skyrocket. Primers can also make a big difference in pressure.
Since the exact recipe has to be used they're not hard to put together, but finding the right combination of components can be a little exasperating, one reason I depend on Ballistic Products so much. They also offer very reasonably priced loading guides with LOTS of combinations, and very good information.
