Not a clue. I don't have that problem with my Uberti or Pietta guns. My chambers just have the sharp edge removed not deeply chamfered. Perhaps the problem is if you are shooting heavy loads. In my .44 I use 18 to 20 grains volume of FFFg GOEX. If you are using the "P" stuff or 7cubed that may be the problem.
If you can't get real Black Gun Powder you might try APP, Black MZ, or Jim Shokey's Gold which is the same stuff with a different label. It is a different chemistry than the "substitutes" but works well using VOLUME equivalents not weight.
Produces less fouling than real BP, does not like compression, but might be easier to find.
It does not work at all in flintlocks so I am told.
Good luck
Bunk