Round groove's as Mike said. Also, if you're tackling a HVF you can't go wrong getting yourself a copy of Tom Grinslade's book Flintlock Fowlers, the first guns made in America. You will find 33 different HVF's with multiple pics of each showing key dimensions and details thru the evolution of the HVF. Being from their region I had the opportunity to hold, handle, and measure originals. Most will not have that option. Still, I wish I'd had Grinslade's book as an adjunct back then in the early 90's when I was doing my legwork. HVF's are an expensive build, 'planning is key and info. is the key to that. Best of luck, keep us posted on your build! p.s. Bore's range from .70 to .80 cal. on originals, so..., 12 ga. not 20's and 16's. Cheers, Fred
