Robby
These barrel features in combination, are typical to both Dutch pieces or those made in Liege around the 1740 time frame. I have a pic of a Behr. Although this barrel is not near exact, the combination of features; oct to steps, wedding band to round with another band then a muzzle bell, is to a 1740 Dutch flint breechloading turnoff pistol by Behr. But thats a complicated build and the whole pistol is shorter. But an optical illusion could be made into a muzzleloader; but the length of this barrel would be off.
Using this barrel, a standard Liege Dutch holster pistol config for this length would be somewhat correct (or close) for around 1740, but she's gonna be a heavy one, no matter what you do! Do you know who made the barrel?
Hope this helps.
Susie