Powder Potency

[Sevendozen]

So, I've tried to do a bit of research before I asked this, but I don't seem to be finding my answer.

Does powder lose its potency?

Please note that my question is not whether it will still go bang or not...it will, and it does. My question is the possibility of diminishing potency of that powder over time, while still in optimal conditions/temperatures. Does it get weaker? Does it burn faster/slower or less efficiently?

 

[Grenadier1758]

Keep black powder away from moisture and it doesn't weaken. Substitutes may weaken. There are some who have used substitutes after long storage who claim little loss of power. Most will tell of substitute powders losing strength in the course of one hunting season. I wouldn't worry about losing powder with real black powder.

 

[Erwan]

For now two month I'm shooting an old black powder from the end of the seventies, I found it in the old material of a friend of mine who is/was gunsmith now retired since a couple of month...
The quality of this powder was not the finest in this time but this is now exactly like at this time (yet this powder is no more existing for a long time in any shop) : the black powder can stay very, very long time in the can or bottle and work like at the first day...