Not exactly a long rifle but my DIY perc O/U shotgun ---
1960s our group 'Long Island Black Powder Rifles' decided to shoot shotguns. Friend had given me a 12 ga. Belgian 12 breakover double with stock broke off I decided to convert to perc. The pictures are pretty much explanatory, where the stock slides up between the two parallel tangs, etc. Locks were new-old-stock from Dixie & the triggers,etc. from the old shotgun.
Engraving I did about '75 when I decided I had to learn to engrave.
"In for a penny, in for a pound" I might as well show it all - patches: