One: Just because deer are in your yard does not mean you can legally shoot them with anything! You have to be licensed, and it has to be deer season!
Second: The Kitchen is about the worst place to store a BP anything- the worse being in your bathroom next to a shower. Too much humidity in the Kitchen from cooking and boiling water, etc.
If you have a Cool, DRY place next to the Kitchen, or near the back door, you can store a BP rifle fairly well. Don't put it up near the ceiling where heat rises and take household humidity up with it. You can tape the muzzle of the rifle to keep moisture out of the barrel. And you can grease the bore after seating the PRB to protect the barrel from rust during storage. At the other end, find a pistol casing that fits over the NIPPLE AND PERCUSSION CAP. Consider buying an O-ring at the hardware store that will fit over the nipple, but sit low enough that it won't interfere with seating the cap on the nipple. Then choose something line .380 or 9mm casing to place over the nipple and cap, that will have its mouth sealed by that O-ring. You may have to trim the casing to let your hammer come down far enough to rest on the top end of the casing, and hold it in place.
That casing will serve to seal moisture out of the nipple, and access the powder charge in the barrel. It also acts like a 'man-made' Safety, keeping the gun from firing if it gets "bumped", or knocked over. Tie the casing to the trigger guard with a small cord or leather strap.
To fire the gun, just cock the hammer, lift off the casing, aim, and fire. The tape on the muzzle will be blown off by the air in front of the PRB before the PRB reaches the muzzle. :thumbsup: