Friend Oyvind,
Over the years I have handled and examined an untold number of original Southern rifles as well as a like number of Pennsylvania/Kentucky rifles.I have never seen a peep or receiver sight on any rifle of this era.You do find them in the caplock period on rifles used in match competition and long range shooting,ie buffalo hunting,but here you are talking the 1840's+. Southern rifles were still being made in the Southern Mountains even up into the first quarter of the 20th.century,but still,no receiver sights to my knowledge.( Notice that I say "to my knowledge",because as surely as I say absolutely no receiver sights,someone will come foward with one!)
The concept was present,however.I have examined a number of 17th and 18th century Spanish weapons coming primarily off shipwrecks here in Florida,and a rear sight in the form of a small tube several inches long is very common.These are very effective in creating the same sight picture that you get with a modern receiver sight.
A sidenote that may interest you since your background is early military history is this: Our WWI hero,Sgt.Alvin York,is always pictured with a 1917 Eddystone rifle.Even his statue in Jamestown,the county seat of his home in Pall Mall,Tennessee shows him with the Eddystone. He did not,however,use this rifle.When he landed in France his Company was given the choice of keeping their issued Edystones or swapping them for a regular issue Springfield 1903.He wanted the Springfield simply because,in addition to a receiver sight(which he strongly disliked)it had a regular notched rear sight with a post front sight like he had grown up using in the Tennessee Mountains.
The peep sight that you have shown HAS caught my attention,however! Now that I'm older than dirt and almost have to have my rear sight a couple of inches from my front sight,your illustrated sight looks like the answer! I think I'll get one made and slip it on one of my squirrel rifles and see if it puts me back in the ballgame
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