Thank you all for your input. Alot of food for thought.
Chambers lefthanded mountain percussion lock was the smallest lock I could find. I think its possible to modify it to fit.
The plate measures 4 3/4 x 15/16, which makes it 1/4" longer and 1/16" taller than the original Fleeger lock. From the pictures I've seen of the chamber's lock, I think can take 1/16" of the bottom of the plate and reduce the length with 1/8" .
Deciding what to do with the breech is my toughest problem. The mountain lock is made to fit a 1/2" drum, so installing a drum on a flint patent breech sounds like the best solution. The barrel I've bought is 1" at the breech and threaded 3/4-16. TOTW has one flintlock patent breech that will fit.
http://www.trackofthewolf.com/Categories/partDetail.aspx?catId=14&subId=143&styleId=515&partNum=PLUG-FH-16-3 . It's a Hawken breech. I have searched other suppliers and not been able to find any other options. The tang would have to either modified or a new one welded on. What I like best with this solution is the thick wall on the patent breech that allows more thread depth for the drum. The wall of the patent breech is 0.3575" thick. The barrel wall is 0.250" at the breech.
Comments, ideas or suggestions for other solutions welcome. Lucky RA, thanks for the extra measurement data. I'll be using the stock pattern I got from you and every bit helps. You mentioned that a hooked breech might make the rifle look beefy. Would modifying the tang solve this?
Best regards
Rolf