The critters responsible for eating holes in horn buttplates and grip caps are the larva of the carpet beetle. They are also a real problem to knife collectors who own knives with horn grips or scales. Since they like to eat horn (and hair and skin too), they can also destroy taxidermy mounts, and even the powder horns used by those who shoot muzzleloaders. Moth larvae get the blame for holes eaten into wool clothing, but carpet beetle larva probably do more damage. Naturally, wool carpets and oriental rugs are also on their menu.
https://www.knife-expert.com/bugs036.txtPrevention is the best cure, and there are a number of pesticides that can control and kill them. Permethrin might be a good choice to spray onto the carpet in your gun safe, since it is fairly safe around humans. It is the pesticide that is commonly used by hunters to treat hunting clothes to kill ticks, and is also used on dogs, horses, and cattle for the same reason. I use the 10% Martin's Permethrin, and dilute one part of the pesticide with 19 parts of water for a 0.5% solution to treat my hunting clothes and outdoor work boots and shoes. You could also dust the bottom of your safe with diatomaceous earth.
