Corrosive Ammunition

From GunCounter

Corrosive ammunition is a term that is used to denote military-surplus cartridges that use a potassium perchlorate or similar priming compound that leaves a hydrophilic salt residue in the bore upon being ignited.

This residue aggressively absorbs water from the air, and traps it on the surface of the bore, resulting in rust.

The easiest and simplest way to remove this salt fouling is to flush the bore of the rifle using hot, typically soapy, water in large quantities. Various Blackpowder solvents also readily remove the salt residues. Many modern solvents, however, do not readily remove the salt residues.

Discussion of cleaning after shooting corrosive ammo is available at Surplus Rifles.com

Corrosive ammunition is inexpensive and good, but the rifle must be cleaned after being fired without fail or unreasonable delay.