I was out of muzzleloading for a while, and got back in during the 1990's. I found there were caliber-specific cleaning kits available, so I bought one. It included a brass bristle brush. In retrospect, my dad had told me many years ago that these brass brushes are designed to be pushed
all the way through the barrel and out the far end, meaning they should only be used in "britchloaders," as he described them, or in muzzleloader barrels that had the breech plug removed. Pushing it all the way through allows the bristles to relax and then reverse. However, dad was long gone by the 1990's, and I innocently pushed a brass brush down the bore of my new muzzleloader and could not pull it out. I ended up clamping the rod in a vise and jerking the gun off the brush. It came out, after blessing it with some most canonical execrations, as well as some comments regarding the parentage of the stuck brush, but I think I learned my lesson. These brass brushes, I believe, are designed and marketed by people who likely have very little real-world experience with muzzleloaders.
One of my references, dating to the 1930's recommended using a bore brush for cleaning muzzleloaders, but the author also indicated that bore brushes at that time were made of hog bristles. I guess you could call them "boar brushes." These natural fibers would be soft enough to reverse direction, especially if you give the brush a twist while you are pulling. As far as I know, natural fiber bore brushes are no longer available. Too bad. Seems like these would be another source of revenue for the swine industry, and we shooters would have appropriate bore brushes for our muzzleloaders, but I am still waiting for industry leaders to ask my opinion.
The best we can do now, if you are determined to use a bore brush, is to use one with nylon bristles. Even these can sometimes be hard to reverse, although if you clean your gun with hot water, dipping the brush in it for a few seconds will help soften the bristles a little. You want the kind that have the twisted wire securely fastened to the threaded base, like these heavy-duty brushes from Brownell's:
You can see on the bottom brush in the image how the wire is in one piece, and passes through the threaded shank. These won't pull off, although you'll want to make sure the threaded tip of your cleaning rod is cross-pinned.
I still use a nylon brush occasionally, although I don't necessarily think it would be required for a good cleaning. This is usually for guns that will be put away for a while.
Best regards,
Notchy Bob