Sir,
Octagon to round is not the correct barrel profile, it should be round from breech to muzzle. The barrel as shown currently on S.F. website illustration for K-5 Light Dragoon Bess, while may work for the S.F. kit, is not correct geometry for an English musket.
If you are interested in a British Officers Model Musket (Rogers Rangers) would reccommend that you contact Larry Zornes of the Mold and Gun Shop, 6493 S.R. 139, Jackson, OH 45640. From his last years catalog:
"British Officers Model (Rogers Rangers), round face lock, 16 gauge smoothbore, walnut stock, brass mountings with sling swivels. Formerly belonging to North Star West".
This modern model was developed by Curly Gostomski of North Star Enterprises, went to North Star West with Matt Denison, and now resides with Mr. Zornes.
Mr Zornes has the lock listed seperately in his catalog also as "Rogers Rangers Round Face".
If this is of interest would encourage you to contact him directly. His advertisements are in Muzzleloader Magazine. Will send PM with his tx number.