Solid lead ball for 2.25 inch is about 2.2 #.
It is a little over N-SSA weight for such bore size. I use it, but keep charges way down. I have no reason to use max charges anyway.
With shot, you will need a wad of some sort.... possibly an inch or so of plywood cut to bore size with a hole saw. Remember that the wad is part of the projectile weight, so weigh it and add it to your total weight.
One thing that scares me about shot, although shotguns use it every day with no issues, is the possibility of it somehow jambing up in the bore and causing pressure to increase. A load of "00" buckshot has the same problem, and it works every time, so my fears are probably unfounded. Shotgunners seem to go by shot weight, and don't seem to care about shot size as far as pressure goes. An ounce of shot is an ounce of shot, be it #9 or some "000". It seems to work for them. Is my fear imaginary? Possibly. I am pretty sure that if you fill a pipe with shot and hammer it in there it will get stuck solid. A solid round ball ... probably stuck way less solid.
Unless you are being attacked by a neighboring country, these guns have the capability of way more power than is needed for simple target shooting. Big blanks are a blast, but live loads, why push them? Go light, save stress on your barrel, carriage, powder costs.
