Might this help

[No Powder]

Last flintlock I purchased had been rode hard and put away wet. Bore isn't real bad, but not real good. Accuracy is sufficient for deer hunting. But still, I think it could shoot tighter groups. Thinking about trying several things. Bigsmoke mentioned pressure blow by in Winter Hawks situation. Being my bore is not in perfect condition, I'm wondering if I could be dealing with the same thing. I know there are different things I could do to correct that, if that's the problem. I would like to try loading a fired patch on top of the powder before loading the prb. I generally pick up my patches at the range, so I've got a lot of them. This would be the cheapest solution if it helps. Has anyone ever used old patches on top of the powder? I know I could use wads, thicker patches, larger balls and other things, but cheap is the key word. Appreciate any opinions and suggestions.

[doggoner]

I purchased a "rode hard and put up wet" 50 cal. I used the leather from a discarded recliner and a harbor freight 1/2 inch punch  and the results were amazing. I had some bear grease and lubed the patches will it. Used them over the powder and went from peach basket groups to under 2 inch groups. YMMV. Good luck.

doggoner

[No Powder]

Now that's what I'm talking about. Thanks Dennis.

[Bigsmoke]

FWIW, in testing our big bore rifles, I found that with the "noticeable" powder charges we were using, the patches were totally burned and in tatters after firing.  Seeing as we were making rifles out of shotgun size bores, the idea struck me that lubed cushion wads for shotguns would fit just right in the barrel and protect the patch when fired.
Our results were that the patches could be used over and over.  I did get 4 shots out of a patch and it still looked good.
Noticeable = 200 grains Fg up to .72 caliber, 300 grains Fg for the 8 bore and 400 grains Fg for the 4 bore.
Gee that was some fun shooting.
So, bottom line is regardless of the caliber, if you can fashion some sort of wad to load between the powder and the PRB, you will accomplish three things.
1)  You will seal the powder from burning the patch
2)  You muzzle velocity will increase
3)  When loading, especially with the cushion wads, you wipe the bore before the ball goes down and the fouling greatly decreases.  I once shot a 20+ shot trailwalk with my .69 caliber rifle running 200 grains of Ffg and never wiped the bore.  The last shot loaded as easy as the first.