I’m putting a 45 caliber round ball barrel on my TC Seneca. It’s a spotless .36 caliber squirrel rifle and one of the best carrying little guns I’ve ever held. I’ve got a cut rifled 13/16” Green Mountain barrel blank and am fitting the breech plug right now. It’s rifled to 1:66” for round balls and is 36” in length, although I’m going to shorten it up to keep the rifles balance. Once I finish fitting the breech plug I’ll dovetail the barrel for the underlug and sights. When that’s finished I’ll use silver solder and install the under rib and thimbles for the ramrod, then rust blue it as the final touch. It will take a couple 2-3 weeks but should turn out very nicely. I almost went with a .40 caliber barrel but I’d rather have a 45 for deer. I’ll try to get some pictures of the rifle and my progress posted as it progresses.