Old (100 year plus) 97 survive cowboy action with regular trap loads just fine. If your range is being picky about shells and you don't reload you can try wax slugs or cut shells. A wax slug is when you pick open the crimp on a shotshell and pour hot wax onto the shot then fold the crimp back down. I don't know if that works without a press but maybe you can MacGyver something. A cut shell is when you use a jackknife to cut 90% ish of the shell through to the wad so that when you fire the shell everything forward of where you cut goes downrange. This is somewhat risky because there's no guarantee the outer hull will leave the barrel. There are buckshot moulds you can buy so you may be able to buy a cheap single stage press, pick open the crimp on a shell, melt down the shot, then reload however many pellets you get out of the shot. Just a few more pennies for you.
