Re: German Surplus
"The compound used in the primer - fulminate of mercury is what makes it corrosive."
NOT quite, son.
Your arms and ammo and technology and chemistry info is stuck in the cowboy days. The first big "change" in primer chemistry was more than 100 years ago, with the move to "non-mercuric" primers which were based on one of the chlorates* (ammonium or sodium, I don't recall as it was before my time) as an oxidizer and some sort of fuel.
Mercury fulminate was okay for black powder cartridges getting a few reloads, as their 10-20KPSI pressures didn't really compromise the strength of the brass IF they were washed out shortly after firing. Brass + mercury was a disaster with smokeless cartridges.
Sodium perchlorate is, chemically, table salt with a bunch of oxygen added to the molecules in some structure I don't remember precisely right now. All of these oxidizers, like NaCl, attract water like a sumb**ch, and make things rust even in pretty low-humidity environments.
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* I worked one summer at a chemical plant which made ammonium perchlorate and ammonium chlorate. The water solution of either salt, if spilled on your clothes, will turn the cloth into a large strike-anywhere match! A few years later after graduating college, another local factory making the stuff had pretty much all of their inventory from the buildings to the loading dock blow in a series of explosions sparked by--what else--a pair of welders who were careless on a job in the DRYING ROOM of the plant.