got a 4 point this year with the load that was still in the gun from last year and this is south fl with the rain and humidity almost everybody i know here does the same thing as long as the barrel is clean to begin with leave it loaded inlines with 209s are hard to beat ..
I would never trust a load from one season to another weather it was using a standard cap or shotgun primers. Yes, it may go off but the powder may of been compromised by the humidity or any other type of moisture. That is the nice thing about black powder, it usually always goes off one way or another. I watched a hunter kill a beef cow just that way one year. It had been raining for a couple of days. When he got back to his truck he decided to fire the rifle and clear the bore. He pointed it in a safe direction and fired it. The 209 primer went off but there was no big boom. He held the rifle in a safe direction for about 2 or 3 minutes, he then turned the rifle in another direction to place another 209 into the rifle. Just as he held it up to place the primer in the rifle went off. There were a few range steers standing about 100 yards away in the direction that the rifle was pointed. Just after it went off and we all looked at him one of the steers dropped.
You should of heard him trying to explain that to the rancher when we found him. He didn't get a deer but he did end up with some range beef for a few hundred dollars.