It was my understanding that all Berdan type primers contained a "salt" type compound. Thus they would all be somewhat corrosive. Is this true? I've seen the posts with complaints about South African ammo being corrosive. Is this why?
IB- Origionally, primers were made of Mercury Fulminate, and a bit of Potassium Chlorate.. Known as "Merchuric Priming" this was fine in black powder weapons, where the mass of fouling would tend to hold the resultant salts..No problem..(Mercuric priming has it's own problems with brass life, and reloading, but that's another story..)
When smokless powders evolved, the salts generated were not held as well by the much smaller amount of fouling generated.. Given a bit of humidity, and you'd have a nice bit of corrosion..
Modern, (Post WW2) priming compounds for the most part are non corrosive.. This does not mean that no bore fouling, or rust will occur if left uncleaned, just that the priming will not be the reason..Currently, Lead Azide is one of the primary constituents of priming compounds..
EROSIVE priming compounds, and propellants are still found. Cordite is a good example..
I have seen rust develop from "non corrosive" priming compounds, usually when the weapon in question is not cleaned and left in a humid environment with significant propellant fouling present.