"Incidentally, the reason the US kept corrosive primers through WWII was that the then relatively new non-corrosive primers had not been sufficiently tested for long term stability."

I've heard that one but I'm not so sure if it's true. The exclusive use of non corrosive .30 Carbine ammunition during the war creates doubts about that statement.

I was thinking that maybe the military just figured that with all of the corrosive ammo already in the system, it would be too hard to issue just non corrosive .30 caliber ammunition to troops during a war. Soldiers could be carrying both types and would end up with rusty bores regardless. Why complicate the ammunition situation?

The Carbine ammo was non corrosive from the start and mixing corrosive and non corrosive ammo wasn't possible.