I saw a very interesting frlintlock rifle the other day. It was a "Ketland" flintlock rifle made approximately 1780 according to the owner.

It was a fine looking rifle and in very good condition. What was unusual about it was that it could be loaded while you were lay down.
The backsight was about 1-1/2" wide by about 1/4" thick and about 1/2" high. It could be unscrewed and was attached to a large threaded plug. The ball was inserted into the barrel and wadding was put in behind it. It appeared to have a slight taper at the breech to stop the ball rolling out. It wasn't patched.
The powder was put in at the rear of the opening where the sight/plug went and then was fired like any other flintlock.

I have tried to find out more about the rifle but I only get the maker,W.Ketland, who was based in the Midlands, the actual model does not come up.