One thing with spar varnish is turning black. Old ships often had unpainted but varnished wood, we remember them as ‘black ships’ but they started out brown.
Since your gun lives indoors this won’t be as much of a problem but is something to think about.
We don’t know for sure why it was the Brown Bess, one idea is it’s reddish or yellowish brown finish over the dark finishes on many other muskets of the day
Tru-oil by birchwood Cassy should give you close to the finish you want. It’s a oil-varnish mix. It’s shiner then I like, but will give you a very buffed looked.
Even if your all thumbs it’s real easy to do your self. Often jobs that look scary are infact pretty easy, and your thumbs turn in to fingers pretty quick. And lots of you tube videos can walk you through.
) The trouble with Tru Oil and modern finishes is that they don't give the warm soft look of linseed nor do they bring out the grain as well. If you start with linseed you can always add a Tru Oil or varnish finish later after the linseed has set for a few weeks and you want a more water proof finish. You can get the soft glow finish with Tru Oil or varnish later but that's where a little learning comes in.
