One of the benefits of shotshell reloading is that there isn't any "working up" of loads. Pick the data, follow it exactly, and load it up. The downside is that each load is specific in its components. No switching out primers or hulls. A simple primer switch can raise or lower pressures dramatically.
The steps are similar to metallic reloading. Inspect the hulls for defects. In 12ga I typically see splits at the crimp. Deprime and reprime. My press resizes the base but I've never seen the need for it in target loads. Powder drop. Insert the wad. Insert the payload. Crimp.
In picking the data to follow I start with the hull. I stick with one as the press must be adjusted to that hull. A press setup for Win AA probably won't work on Rem STS hulls. For this conversation lets use Win AA. Next pick the payload and speed you're targeting. Let's say we want a heavy target load. 1.125oz at 1200fps.
Now go to
www.hodgdon.com and go to the reloading data page. Then enter the data in the dropdown boxes. 12ga, 1.125oz, Win AA. Click "Get Data" and a huge list will populate. Hmmm, where to go from here? Couple things I look at. I try to keep pressures between 9,000 and 10,000 psi. Easier on the gun and easier on me. Another is powder. I try to keep with the mainstream powders that can be found anywhere. Clays, Titegroup, WST and the like. So scroll down and let's see what WST has to offer.
There's a couple that look interesting:
20.0gr of WST, Win 209 primer, Win WAA12 wad, 9,800 psi.
20.5gr of WST, Win 209 primer, Rem Fig-8 wad, 10,000 psi.
Good as place as any to start. Load a few. Shoot some patterns to see how THAT load work in YOUR gun. Like metallic reloading every gun is different and nothing but putting lead to paper will tell you how it works. Not all wads work the same. Some open quickly, others slowly. In this case a wad switch would not be a big deal at all.
I said earlier that substitutions are not allowed. There are exceptions. {Isn't there always.} Noblesport primers are a direct 1-to-1 interchange with Win 209. This is published in the loading manuals. Clones of the wads are interchangeable. For example a Claybuster CB1118-12 is a direct replacement for the Win WAA12. FWIW: I use Claybuster wads and Noblesport primers. Much cheaper than Winchester.
Last item is the payload. The shot. That's somewhat up to you and what you're doing. For Trap and Sporting Clays it's either size 7.5 or 8. Skeet it's 9. The larger pellets will fly farther but you will have fewer of them to send downrange. Next is the decision whether to use magnum or chilled shot. I use magnum as a touch of antimony is mixed in to make the lead harder. Harder pellets are less likely to deform and will fly more true. Brand really doesn't matter.
If you want to load buckshot or slugs then that's a whole different animal. A bit more specialized.
