Winchester 209, 75 or 80 grains fffg, 1/8 " over powder wad, 1/2 inch cushion wad, 1 1/8 ounce shot, over shot card wad.
The load above should produce about 4,000psi + or - 1,000psi.
about half of what a smokeless load would.
In the 2 3/4 inch loads I use for skeet I use 68grs. (2 1/2 drams) FFg, 2 nitro card wads, 1 .5 inch fiber, and 2 more nitro card wads under 7/8oz. of shot.
In a cut down hull just use what ever combination of card & fiber wads is needed to get a good crimp. The only other rule is use at least one Nitro Card wad directly over the powder.
If you use Black Powder, card/fiber wads & lead shot, and your gun is in good condition pressure will not be a problem.
You can also use plastic wads with Black Powder (CB1138-12) but then removing the plastic-powder fowling can be a pain.