I built a muzzle loader from a kit a long time ago @78-79.
All it took was woodworking tools and some files.
Stock was semi-inleted, I used wood gouges and sandpaper wrapped around a dowel to fit the barrel.
The rest of the parts were fitted with various X-acto tools.
The octagon barrel was in the rough and had to be draw filed to smooth and prepare for browning.
I would assume the kits today would require much less fitting