Forget everything you have learned about muzzleloaders, when you use blackhorn. Blackhorn is a nitrocelulose base powder, (modern smokeless) it's no more corrosive than a centerfire or shotgun. 
Forget what I've said, Blackhorn will rust your whole gun, don't use it it's junk. There now i'm just like the others who have never really tested it.
Forget everything you have learned about muzzleloaders, when you use blackhorn. Blackhorn is a nitrocelulose base powder, (modern smokeless) it's no more corrosive than a centerfire or shotgun.
Not true! There is sulpher in Blackhorn 209, and the fouling residue can and will trap moisture, causing corrosion under certain conditions. If you don't get a good burn from either poor ignition or leaky primer pocket, even more so. Humidity will also play a big roll.
If you don't believe me, you can read the MSDS on Western's web site.
I have witnessed some premium stainless steel barrels that rusted from BH209 residue being left in them. These were muzzleloaders that no other powder was ever shot in. I use BH209 pretty much exclusively these days, but if you shoot them, you need to clean them. If you don't, you take your chances with whatever happens. Sure, you might get away with no problems some of the time (if conditions are perfect), but I guarantee you will not be so lucky, all of the time. A couple of these rifles were left uncleaned for less than a week. I have also seen what I would call etching in the bore after just a few (4) days.
I love Blackhorn 209, but if you love your muzzleloaders, clean them after shooting.
Not true, or you really don't know. I've done all the tests, I know. Some people just like to debate. Their are other reasons why barrels rust, but it's not that powder. Most people just repete what the've heard as truth.
You need to talk to people that have really tried it. Then you will get the right answers. 
Ask the person dogging, if they use it.
I have tried it many times burned up several jugs of it and I have not had any rust issues because I clean my gun thoroughly after ever time out with that powder and I read the original patent application and am smart enough to know it has corrosive ingredients in it and not dumb enough not to clean my gun afterwards. I could care less what anybody else does with their guns but I will make a mental note not to buy a used muzzleloader from anyone that advocates you don't have to clean your gun after shooting bh209.
Yup you guys "know" it all. I'm the stupid one. I'm not dumb though, cause I can talk.
It's odd that all the people that have positive results and feedback with blackhorn are wrong. 
Sorry I ruffled your feathers, but what you said, and now changed (added to) in your first post is just WRONG!
Let me give you a little background of my experience with Blackhorn 209. I was the first person in Michigan to own a case of this powder when it became available, way before any retailers. I have shot several cases of the stuff, through no less than 15 different types of rifles, pistols, and shotguns for 4+ years. This would also include 40+ different breech plugs, from OEM, modified OEM, and several custom breech plugs , some that I helped develop. I have tested it from one end of the spectrum to the other, and beyond.
You won't find a bigger proponent of Blackhorn 209, than me. But, you won't see me making the statement that you made in your original post.
I have nothing but positive experiences with Blackhorn 209, because I have tested it thoroughly, know it's limits, and requirements. A simple search of this site or others will back up my claims.
You made a "blanket statement", there is no absolute when dealing with several types, styles, and brands of muzzleloaders. While one guy, with one rifle, in one climate, may get away with not cleaning his muzzleloader, in no way will everyone.
How many cases, or should I say jugs of Blackhorn 209 have you shot? And, through how many rifles?
And you are right about one thing, people do like to debate, even when they are WRONG!
