There are NOS preban AR-15 rifles floating around. They are spendy but you said that price isn’t an issue.
I agree with Mac; it is difficult to give you an answer without knowing the purpose of the rife.
They have a rattle in the transfer bar that is mildly annoying to some.
I replaced the front sight with a night sight and thought it was a worthwhile improvement and it was easy to do.
XS Sight Systems, Inc. - Products - LCR
It is a great little pocket carry gun.
You can also check the lever pivot screw and make sure that it wasn't tightened by a gorilla. They can be over tightened to the point that the lever won’t move. From your pictures I can see that the lever pivot screw has been in and out. So you can check that.
Kroil it as recommended and let...
Everyone is going to dry ball sooner or later. The best thing to do is not to let yourself get interrupted during the reload cycle so you don’t screw up.
On a percussion rifle you can pull the nipple and drop a few grains of powder in the bolster, replace the nipple and shoot the dry ball out...
Use real black powder in a percussion or flintlock rife. Real black powder has a lower ignition temperature than any of the substitute powders.
I have never had a misfire using real black powder (GOEX or Swiss) even when hunting in the rain.