When I shoot my 50cal rifle, I notice a red substance in the fouling deposit. Could this be a sign that my black powder is not dry?

Are these little red specks? It's believed that it's precipitated red sulphur, although even Bill Knight aka Mad Monk, isn't sure. It's one of those little mysteries that I've stopped worrying about.

Bye
Jack

I've been told that the red fouling is a sign that the powder is burning at it's peak effeciency when it produces it. It is a sign that the load is about right. Usually lighter or heaver charges will not produce this stuff.

Haven't I heard or read something like "dragon's blood"?..can't remember where...but the idea is that under certain circumstances, the sulfur leaves some more complex percipitates that are red in color (of become red when moisture gets to them).

I've heard that term too.
I haven't seen it in my guns, but I understand it usually shows up when using rather hot loads and most of my shooting is at paper targets that don't take a lot of knock down power.
Now that I think about it, I haven't even seen it in my Schuetzen and that's a fairly stiff load of 70 grains FFg behind a .40 cal paper patched 400 grain slug. (yes it is a muzzle loader).