One good source would be Dave PURINTON, owner of the Brunswick (ME) Gun Shop on Bath Rd. in Brunswick - although I'm told he is on medical leave-of-absence for the winter. One of the resident 'smiths might know a bit about it.

I have a copy of "The Muzzle-Loading Cap-Lock Rifle" by Ned ROBERTS (1940) but he seems to deal with American arms and makers exclusively.

As I recall, the British Navy used Brunswicks for a while from the 1780's up through 1850's, when the "Enfield" became the standard for land and sea forces. I'm not sure but what that BBC series "Sharpe's Rifles" dealing with the Napoleonic Wars featured flintlock Brunswicks in action. Yours seems to be a civilian edition.

This system uses a very distinctive "belted" ball, which looks a little like a tootsie-pop without the stick.. and made of lead, of course. I think you can still get moulds for them, although I have learned over 30+ years of dealing with "Dixie" GW to be extemely circumspect when doing so, and then only as a last resort.

Does your rifle appear to have been made as a percussion lock, or converted from flintlock (as many were)?