A lot of mold on gun stock wood is caused by old, multiple applications of 'raw' linseed oil.
It was the go-to gunstock finish for many decades and many still like to use it.
It doesn't really oxidize and harden much over time, so like any other vegetable oil that it is,,it goes rancid and mold can result with the right conditions.
Not uncommon at all to find mold in older gunstocks inside the inletting. On the outside of the stocks if they've been left untouched and in a darkened space for a time.
What ever you do, it's best to first remove the wood from the metal of the gun.
If there's mold on the outside,,there's likely mold inside the inletting as well.
Plus, if you treat the outside mold condition with something like Bleach and get that onto the metal parts,,the bleach will take most any metal finish off the surface as well.
Bleach (sodium hypochlorite) if it gets down into the wood and down inbetw the wood and the metal parts in the inletting and left there can cause severe rusting to the metal as well.
It's a powerful oxidizer.
The chlorine in the bleach kills mold on hard surfaces but doesn't penetrate into porous materials . The chlorine stays on the surface so mold can continue to reappear. It's good for hard surfaces like tile, ect.
The same goes for ammonia, vinegar and oxalic acid (wood bleach). Their chemical stays on the surface and kills the mold there. But doesn't penetrate deep enough to kill the mold down in the wood so it reappears.
For wood and especially a gunstock, Hydrogen Peroxide is a better choice IMO. The OTC stuff from the drug store.
Brush it on and scrub lightly. Let it soak in. Reapply if you want to. Rinse and let it dry. It may lighten up any mold darkened spots as well as kill the mold on the surface and down in the wood.
Any removal of mold on wood generally also removes any finish that was once there. Actually the finish is already gone as that is what the mold formed on and fed off of,,the rancid oil in most instances.
A little touch up to the finish when done can bring the looks back in line. Certainly better than a mold covered piece of wood.
All the above is for conserving the wood,,killing the mold and getting it to stop from reappearing.
If you just want to wipe it from the surface of the assembled gun and make it look nice for the time being. A simple spray and wipe down with most any of the gun oils on the market will do.
But the mold will likely return at some point. Especially if the storage conditions are right for it's re-growth.
It's still down in the wood.
