Leviathan, I've seen these on "crude work" and on arms with good architecture.
1) no finish - Dixon's had a fine old Bucks looking rifle never stained or finished - lock, stock, barrel, trigger and guard and one or two pipes, wood shaped with coarse rasp. Converted to cap and continued use, after 200 years was a weathered gray like barn wood. I built a copy, painted linseed oil on butt and down ramrod hole, still in white after 20 years, dirt and fouling make the curl show up real nice. Draw filed barrel has taken on a nice mottled brown.
2) no finish, burnish with something smooth and hard - furniture still finished that way, shows curl.
3) Herschel smeared axle grease under some mounts to resist damp - could try all over, messy.
4) anything used for harness / tack, leather conditioner from the old days - if it smells good, critters might eat your stock. Or mix in beeswax.
5) any paint or varnish that would have been used around the farm or in town. Many old NW guns and plains rifles have a varnish painted on with a brush, right over all the mounts, helps seal.
6) linseed oil or similar, then play heat over it until it smokes, shows off curl and decent finish.
7) play heat over stock without oil, also colors and hardens, like hardening arrow tips.
wax or paraffin probably better than anything else at resisting water, melt paraffin like Wallace and apply warm and rub in. Or shoe wax or other, warm or cold, with or without color.
9) slop linseed oil on wet, let soak in for few days, then wipe off hard with burlap, polish for few days.
10) if blacksmith in south, Wallace and others talk about "black rifles", oil burned onto wood and metal. Ask our southern gentlemen again.
11) experiment, or ask Mad Monk. If email me offline, could send couple pics.
