Hatcher wrote a wholel chapter on Corrosion and Ammunition Developments.
I don;t have it handy, but as I recall, even though other nations had perfectly OK non-corrosive primers, we stuck with the the (potassium) chlorate corrosives, but were going nuts trying to develop a non-corrosive primer.
The "going nuts" part was because sometimes the test barrels would corrode almost instantly, and some would be OK, but sudddenly start corroding weeks later.
Obviously there was another intervening variable involved. Long story short, it was the changing humidity. The test barrels would not rust until the humiidity got above about 50%, and it varied up and down from that quite a bit from day to day, week to week.
Adequate priming compositions were ultimately found, like the familiar lead styphnate... which is now a "bad boy" because they obviously pollute the Erf to the point where no aliens would ever want to take over the planet.
That's how I remember that chapter, so feel free to correct my corroded memory.
And note that this intervening variable (humidity changes) might well explain the vagary about whether a particular ammo is corrosive or not. Might depend on where and when a batch was tested.
Right now the humidity hereabouts (Denver, COmmierado) is about 25% and going down to 14% but will come up and hit 50% about 4AM MDT tomorrow morning.
Terry, "Tireless hunter and killer of intervening variables," 230RN