Stan wrote, "IME, it is mostly trial and error, Lloyd. The "formulas" for really nice patterns are few and far between. A pattern plate is really a good investment, if one is concerned about getting nice patterns out of one's gun(s). What works in one won't necessarily give the same results out of the next (seemingly) identical gun.
Very true and I have used my pattern board to identify some very good and consistent patterns,
I have had some success improving my patterns by using different reloading recipes. Spreader devices, harder/softer shot or a buffering agents can make a
remarkable difference in pattern performance.
My hunting buddy bought a Parker 16 Ga, mfg. in 1917. The guns chokes measured a tight Full and a tight Mod.
We went back to the old way using card and fiber wads + low antimony shot. That combo was pretty good, but still a little tight for his shooting distances. Then, we used two OS cards, cut slits about 3/4 of the way through each card and put them together in an X shape with the shot dispersed equally between the petals. The chokes opened to IC and Mod. RMC all brass hulls were the hull of choice and albeit slow to load, wonderful patterns were produced.
