If you are looking into buying or selling antique guns, you might be hesitant to know whether or not you should clean or refinish the weapon, or replace any parts On the one hand, cleaning it will help to make it look nicer, and show off the different parts of the gun. Replacing parts will help it function more accurately. On the other hand, could doing these things cause the value of the gun to decrease? Whether or not you should worry depends on the condition of the gun and how much it is really worth in the first place. There are some things you should know about how guns are valued before you grab any steel wool, replacement parts, or wood polish.
The most valuable antiques are in factory new condition, which is almost impossible to achieve. Factory new guns have 100% of the original pieces and finish. They essentially brand new, even if they two hundred years old. The gun would have had to be purchased and stored with impeccable precision in order to stay in this kind of quality. However, if you do have an antique that fits this standard, its best not to clean it. You don't want to risk marring any or the original finish. You can leave the cleaning to a restoration expert if you plan to sell the gun.
As you can see by looking at the other antique gun ratings, the level of original finish on the gun does a lot to affect value. For example, a gun moves from "excellent" to "fine" condition based on finish alone. This is why, in general, it is best to avoid giving an antique firearm any type of refinish or scrubbing until you can get it assessed. Your risk removing any traces of original finish, will be move it down in ratings, and therefore down in value. Sometimes, metal parts of a gun will appear discolored with rusty-looking patinas or "bluing", but collectors see both these traits as desirable.
Antique guns really are worth the sum of their parts. Their value is determined based on the rarity of the firearm, the condition of the firearm, and how many original pieces are still present and useable. Guns that are judged to be in excellent, very good, and good condition all will have original parts. However, depending on the rarity of the specimen, the rating may allow for different parts to be used if they are from the same era with the same style and make. Therefore, if you replaced, for example, a defective bolt in a rifle from 1895, with a similar bolt from a rifle of the same make, but a year later, this would be preferable to having a modern replacement, as it still preserves the antique nature of the gun.
It's best to have your specimen assessed as-is before you make any decisions about whether or not it will be worth it to replace any parts. Any parts missing or visibly replaced or damaged or automatically place most guns in the "fair" category, which is the second lowest.
It seems intuitive to expect that guns that are a few centuries old should have few imperfections, but one of the reason why pristine condition is so prized is because it is rare to find an antique firearm that is in such great condition. After all, Civil War firearms were not made to be stored carefully, but to be used. That being said, you should always refrain from buffing out scratches or fixing portions of the metal that have become warped or pitted. These actions will damage the finish, and it is hard to say without looking at the history of your firearm which will contribute more to the value. It is best, if possible, to keep your gun from acquiring any new damage, while refraining from repairing anything until the gun has been assessed.
For more questions about assessing the value of your antique firearm, talk to company that specializes in this area. They will also be able to assist you with preserving the value of your gun, while improving its functionality and appearance.