Originally Posted by
Brian Dick
Nitro powder isn't corrosive. The concerns about corrosive effects on the barrel are spurred by the priming compounds whose residue contains hydroscopic salts as laid out by Bruce. It'll do a number on your barrel if left unattended.
If you see original ball ammo head stamped Mk.VII like your Canadian Dominion Arsenal example, it's going to be cordite powder with corrosive primers. If the headstamp is Mk.VIIz, the cartridge will be loaded with nitro-cellulose powder and most likely have non-corrosive primers but not always. That being said, treat ALL ammo as corrosive and you'll never have a problem with it.