The Hawkins better be a T/C. Other wise Green Mountain Barrels might not fit. They do fit some Lyman and Cabela's but if you have an off brand rifle be sure to check with Kerry at Green Mountain Barrel Company before you order. In flintlocks, all you can find are the roundball and the fast twist. I do think they had a flintlock smoothbore but would not swear to it.

You might have to trim the thimble rib a little. A Dremel tool and five minutes time is all it takes. If your Hawkins is a .50 caliber currently you need a 15/16th barrel. If it is a .54 caliber then you would need the 1" flats.

The 1-28 twist barrels will shoot conicals and sabots excellent. If you want to shoot roundball, then get a 1-70 twist barrel. They are a roundball shooting machine. Get them in as big a caliber as you can if you want to hunt with it. Remember the size of your flats. The .58 requires a 1 inch flat.