This horn was very thick, and suitable to make a nosecap from.
Fill the barrel channel so you don't crush the thin forestock wood while filing it down to accept the cap piece. The paper helps the separate the pine from the stock later on. Two or three thicknesses of paper would have been better than the one that I used. Just use Elmer's glue, or school glue. Don't use high strength glue because you want to peel this out later on.
File the stock to fit the lathe-bored horn. Try the fit, file until you like it.
Prep the horn for glueing in place. With the top of the horn cut away, it's easier to glue and clamp. I used accraglas epoxy, but I think hide glue would be better. It was for the Germans 200 yrs ago. Note: If you're staining your gun dark, color your glue to match your future gun color.
Before removing the pine support block, shape the horn on the muzzle end, and the top flat. This will allow you to drop the barrel in, and shape the outside of the nosecap.
Make some saw cuts in the pine support block. This will lower the cutting stresses on the thin forestock when you start peeling out the pine. The Japanese style pull-saw is a great tool for this, as you have terrific control, and it makes a very thin kerf.
Put the barrel back in, with a big sigh of relief, and start shaping the exterior of the nosecap.
Then, just before you finish the gun, inlay the gold at the muzzle, and heat blue the barrel.