Hi Elk Killer,
Currently, I am working on one, although I have to put it aside for a while. With respect to the lock, you might want to decide what period you want to represent. Many on this forum can list details of what makes an "early" Lancaster versus a "golden age" Lancaster or early Virginia, etc. Yet it seems many lump all English "sporting" rifles and fowlers together as if the styles never changed between about 1650 to the end of the flint period. There were significant style changes over that time span. The first thing to appreciate is that English rifles were built for the landed elite, since they were the only people with access to estates for big game hunting. There likely were no "poor boy" English rifles. English makers did make some rifles for frontier and Indian trade, but even those were of a very high quality. Chambers, Davis, and, L&R round-faced locks are appropriate for English rifles made during the early 18th century up to about 1750. Many early "deer park" rifles were breech loaders using the screw-plug system. The Turvey rifle in RCA volume 1 is perhaps a good example of a muzzleloading rifle from that period. Look at it carefully because it is not shaped like the Twigg and Clark rifles shown in Neal and Back's "Great British Gunmakers 1740-1790". After about 1750, most high-end English guns were using flat-faced locks. Chambers early Ketland with pan bridle would be a good choice for a rifle from 1750-1770 or so. The Griffin rifle shown in Bailey's "British Military Flintlock Rifles" might be a fair example of rifles from this time period. After about 1775, features like roller frizzens, stirrups on tumblers, set triggers, scrolled trigger guards, wrist checkering began to become common. The famous Twigg rifles in Neal and Back's might be good examples. Davis' Twigg lock and L&R Durs Egg lock would make good choices for this period. After 1785 or 1790, rifles often were half stocked, all carving gone, had checkered wrists, locks with rollers on the frizzen springs, patent breeches, pineapple scrolled trigger guards, and metal ribs. Chambers late Ketland might be a good choice for that period.
dave