Cleaning one’s firearms is important to ensure that they will function safely and reliably for years to come. Strange as it may sound, however, it is sometimes important NOT to clean a gun:
Cleaning firearms removes gun powder residue, metallic residue from projectiles, water, and other contaminates. Cleaning guns with a combination cleaner/protectant/lubricant also prevents a lack of lubrication from wearing out the weapon’s moving parts. Failure to clean a gun can cause it to wear prematurely, jam, or even to fail in a way that could injure the user (such as if a barrel becomes so clogged with lead that the projectile cannot properly exit the gun; causing the barrel to explode). In short, cleaning guns is important, and should be a regular part of a gun owner’s shooting practice routine.
When NOT to clean a gun
Having just advocated the proper cleaning of guns, I would also like to note that sometimes it is a good idea not to clean guns; especially semi automatic self defense guns. This is because a gun that has been dismantled, cleaned, and reassembled might have been reassembled improperly by the user in such a way as to prevent it from firing or cycling properly. For example, if a semi automatic shotgun‘s gas piston system is not put back together properly, it will not properly eject the spent shell and load a fresh one, which is a major problem for someone using a gun for self defense. Similar problems can occur with semi automatic pistols, effectively making these guns into one-shot weapons at the worst possible time. This is less of a problem with pump action guns but it is still possible for user error to render such a gun unreliable.
Accordingly, I would certainly recommend that people clean their self defense guns, but that they fire the gun a few times after each cleaning to ensure that it is still firing and feeding reliably. For people such as myself, who do not live out in the country and can only fire their guns at the shooting range, here is one option: Fully clean your gun, then take it to the range and practice with it, then clean only the barrel before storing it for self defense (in other words, fully clean your gun before you fire it at the range, rather than after). It is true that this approach will leave some powder residue and other contaminants in the gun, but this should not be an issue as long as the gun is still cleaned regularly. Most importantly, you will know that your self defense gun is fully functional and ready to fire.