[Ricklin]

I too would start with light trap loads, 7/8 or 1 oz. of 8s. 1050 FPS or thereabouts.
My point is start off with light loads both in deference to the age of the old gun, plus these old lightweight single shots will get your attention, recoil wise.

If you plan on shooting it much keep your eyes open for a 16 ga. reloader. Shooting 16 ga. gets pricey.

Shotshell reloading is a good place to start reloading. No load work ups, it's pretty much a cookbook procedure.

I keep a lookout for a 16 ga. model 12 to add to the herd. Not hard to find a 16 ga. cheap, vs. the 20 ga. which goes for much more.

The 16 ga. Model 12 has a wonderful feel, light and lithe, but has more punch than the 20.