I don't now about the original 1851 Navy .36, but DGW lists the Pietta 1851 Navy as having a tapered barrel with .710" at the breech and .625" at the muzzle. I suppose it is measured across the flats but I don't know that as a fact. This is for a .36 caliber Navy. The faux Pietta 1851 .44 Navies measure .645" at the muzzle. Insofar as the barrel lug width, I have no idea as I don't have a micrometer or caliper.Thank you for taking the time to answer my question, Patbar. Unfortunately I phrased my question wrong. Since the barrel is tapered I am actually looking for two dimensions, the width of the barrel lug at the breech end (not the forcing cone, just the lug) and the diameter of the barrel flats at the muzzle. If anybody has this information it would be greatly appreciated.