RE: POWDER CHARGE LEFT IN GUN FOR TWO MONTHS
I'd say that you should "empty" and clean every few days, at the least.
Now, a story:
Despite my warnings, my brother in law left a charge in his gun from the end of one season to the other. More or less a full calendar year. He took the ML out, the following season, and fired it in three attempts. There was a little rust in the barrel, but nothing like what I was expecting. Heck, I figured that the charge would have never gone off.
Those who wish to appear wise among fools, among the wise seem foolish.
Marcus Fabius Quintilianus (35 AD - 100 AD)