If the Chambers 'Late Ketland' had a mainspring stirrup it would be the 'King' of the English style locks for shure.
Kevin
Why ? It is a great lock just as it is & you can't see a stirrup from the outside.
Its a matter or function and being correct. By the late flint period the mainspring bearing on the tumbler was the hallmark of a cheap export lock. English locks, the better ones, stopped using this method circa 1770s according to J. N. George "English Guns & Rifles".
The link makes the mainsprings action on the tumbler about as frictionless as it can be. Thus a lighter faster spring will do what previously required a heavier spring.
In percussion guns a properly designed link/tumbler produces the "heavy first lifting" that holds the hammer on the nipple better. At the same time amount of force on the tumbler at full cock is significantly reduced and this makes it easier to get a light trigger pull. On flint locks the mainspring force increases as the hammer falls and thus the cock is less likely to slow as it scrapes down the frizzen.
If you get the chance cock a good quality English lock even the later cartridge locks this is all readily apparent.
Dan
