Are #10 percussion caps corrosive?

I believe all ignition "caps" and primers are made with lead styphnate. It is non-corrosive.

While nearly all new production caps are corrosive, the fouling of firing a cap, will attract moisture and eventually the fouled area will rust.

Sherlock,

Did you mean corrosive or non corrosive?

The reason I asked about the caps is simple. I have two MLs. One uses 209s and the other uses caps. I use Hogdon 777 in both. Since using 777, I have just wiped down the guns on the outside and ran a patch down the bores with TC 13 bore cleaner. The TC 13 is for removing fouling and probably has little rust preventatives in it. The gun that uses the 209s is pristine. The one that uses caps has a one inch long section of rust in the bore.

So sorry. I meant to say non-corrosive for most all new production caps. I never fire a cap unless I am prepared to clean as if I had fired a load before storing the gun. I don't even fire a cap before hunting, just patch out to make sure the barrel is dry, listen for a clean sounding passage of air when the patch on the jag pushes air out of the nipple. BTW I'm talking about musket caps and common #10 and #11 percussion caps in a caplock and I've been at it a looong time. But I wouldn't fire a shotgun primer alone and not clean either, But I do not have experience in this part.

TC13 has no preservative in it at all... after swabbing the barrel clean and dry use Remoil or some other type of preservative.

I use Remoil of Breakfree... whichever is closer. Just patch it dry of oil before using it though.

Flatland,

I agree with that for sure. I was wondering about the caps cuz if they are corrosive, then a little more cleaning would seem needed. Again, I note the extreme difference in what happened with the two different guns.