Be aware of corrosively primed ammo. The salts used in the priming , with every shot, will be spewd last down the barrel, after the bullet and powder are pushed out and burnt.
The salts are hydroscopic, and draw water from the air as well as being residues with unburnd powders, will rust with a coating of oil over them.
This priming is not in general use anymore, but American Ammunition made before WW2 and eastern block ammo was corrosively primed untill the 90's, and there are .22lr that are still corrosively primed for deep cold weather biathlon target shooting.
Corrosive priming has the advantage of more reliable ignition in deep cold, something I know it very true.
If you do shoot corrosively primed milsurp ammo, its VERY easy to clean. I use boiling water poured down the bore to dissolve the salts and flush them from the bore. Then a scrub and another flush, dry it and oil it.....done.
Boiling hot water has the advantage of heat , and in heating the steel, its self drying and does so very quickly, and is a quick and simple cleaning. No rust from the limited exposure to water, either.
I used corrosively primed ammo for many years, with no rusting problems at all. Now I do so when using my black Powder weapons, and its a habit I dont regret.
If you use milsurp corrosivly primed ammo, you will need to clean the bore after 1 or 1,000 shots.