The corrosive ammo thread proves the importance. It is a mundane chore that some like and some hate. My buddy has not cleaned a gun in his entire 68 years of life.. it shows too... took me an hour to clean two of his guns.
First.....................history of cleaning guns................Black powder.............shooters soon realized that if you did not clean black powder firearms they either quit functioning.. and/or rusted into piles of shit.. Black powder residue attracts moisture and rust.
Then..... corrosive primers... these were used all the way up till the 70's or even later in some cases... what that means is that the primers themselves contain salts of mercury that when fired.. deposit a corrosive film on metal parts... not good.
Today.... all primers today are non corrosive. This means no harm can come from the primers just because you won't clean your guns.
Second.. powder residue.......... Black powder is not good to leave as it attracts moisture/rust.
Smokeless powder.... from the start it left very little (comparatively) residue ... it would take hundreds or more rounds of fired ammo to actually build up enough to affect function but rust was not a problem.............one thing.. some powders were very 'dirty' leaving mini charcoal briquettes all over the guns action when fired... early powders all suffered from this to one extent or another... Unique was particularly bad and also particularly useful in many loads.
Today.... Most modern smokeless powders burn clean... relatively.. In a revolver you have cylinder barrel gap that can actually close due to not cleaning but you can actually wipe some of this away... it is possible to fire thousands of rounds of smokeless without a failure due to crud. In practical terms it is usually much less.
Bore..... The bore of rifles and pistols gets fouled.. a tiny bit does no harm. Fouling can be jacket material or lead. I have seen 100 year old 22 rifles that were so leaded up that no rifling was visible.. these guns obviously suffer greatly in the accuracy department. Many surplus rifles suffer from jacket material in clumps in the bore.. this also effects accuracy... I once shot a very fouled 98K mauser and got 5 inch groups at 50 yards.. after a day of scrubbing and who knows how many worn out bore brushes the bore was pristine.. the same gun shot inch and a half groups.
lead.. lead will stick to the grooves of a barrel like flies on shit. Removing lead can be a real chore. There are a dozen ways to prevent it and a dozen ways to clean it if you get one.
NEXT cleaning supplies.. what works and what does not and how to use em.