I fouled and loaded my SS Huntsman w/ Hubbard 209 breech plug on Dec 4, never seen another buck I wanted to take, so never fired it during the Dec 5 - Dec 21 Muzzleloader Season. Our Late Antlerless Season started the next day Dec 22 and ran to Jan 1, 2009. The last day of season there were dog tracks all over the woods :evil: , so every deer was ran out of there. At last shooting light, since I wasn't going to see anything anyways, I deceided to shoot out the load. Instant ignition, hit the snowball I stuck on the old dead tree. I brought it home and left it cased in the basement for 2 days. I cleaned it up yesterday, slicker than a whistle. No hint of any kind of corrosion.
My Knight Disc Ext MHC was fired twice on Nov 15, reloaded and hunted with for 2 weeks. Fired out the load at the end of the 2 week season. Excellent ignition, and also cleaned up slick as a whistle.
With that said, I really think I can smell sulfur once fired and I was very skeptical about leaving the fouling in the bore for any length of time. IMO, if you have a very hot ignition, tight bullet, instant ignition, good burn, SS barrel, the residue left is not harmful for 2 or 3 weeks. Of course there would also be several other factors to consider such as, temperature, humidity, weather, storage, previous condition of the bore, stainless vs blued. This was MY experience, YMMV. It is also my opinion that if you are trying to ignite this powder with anything less than the hottest igniton source available, you are not getting as complete of a burn, therefore possibly leaving some fouling in the bore that may be corrosive.
I did some early testing with some #11 rifles, .25 ACP ignition, and some "not-recommended" 209 breech plugs. I know I did not get as good of ignition or as good of a burn with these ignitions. Some of the lesser 209 primers were no better, and in cases worse than these other ignition sources.
This year was a learning year, I know I definitely learned alot, by both my testing and others reports. Is this powder for everyone and their application? No way, but it sure has been great and exceeded my expectations in my rifles. Thanks for all the reports, good and bad!