Home Forums Hunting & Shooting Ask The Gunwriters Vihtavuori powder corroding brass cases

To me, it looks like contamination. For example, sweat, bore cleaner or oil. Part of their response to you was that dampness contributes to corrosion (humidity with impurities). Brass is never completely clean. Traces of what is found in reloading rooms or gun rooms - Hoppes, gun oil, Coca Cola, salt, etc. - find their way onto metal surfaces. For example, you eat some potato chips, or have a bologna sandwich for lunch and don't wash your hands. Traces of your lunch deposit themselves on the brass and bullets. They react with moisture and the deterioration begins. To me, the majority of the corrosion appears on the outside of the cases, with far less on the inside, located at the heel of the seated bullet. This could have resulted from contamination from your fingers,transferred when you placed the bullet onto the case mouth and seating it. Or when the bullets were loose on the table, waiting to be seated.

Deterioration is accelerated by changing humidity in storage. Varying temperature is usually responsible as well. In your case, contamination would be my first check because you said that the temperature and humidity were constant. The reaction is slower in a controlled environment. That is, little variance in humidity or temperature.

If the propellant was the actual cause, then it's reasonable to expect that all the cartridges would shows signs of corrosion.

In the end, you would have to send it to a lab to determine the exact cause. At this stage, it's just a guessing game.