Congrats on a great score! Love my Seneca 45 cal. Accuracy was so so until I tried real black powder, then she started showing off. I used Hornady Great Plains conicals,which, unfortunately, are no longer made. No worries though. Buffalo Arms sells a soft cast bullet that is a close duplicate to the GP conical. I even use 45 Long Colt cast bullets (cast soft) that perform super...250+ grain weights.
One thing to remember: the twist for the barrel is intended to stabilize round ball loads...you have to experiment and tweak the load to get a conical shoot. Do not use the long, super heavyweight conicals....they will not stabilize, and will keyhole, guaranteed.
My magic formula is a 275-300 grain conical, 60 grains of bp and you’re good to go. T/C manual lists 60-80 grains of bp for the Seneca. 60 grains was best, by far. Your mileage may vary.
Enjoy your Seneca....and go kill some deer.
