This may get moved to BP shooting, AND I'm so far from being an 'expert' it ain't funny, but...
The only Trads. I've had a chance to shoot, and clean, were .50, but seemed to have a .25" powder chamber. At least it was a .22 cal brush that seemed to clean them the best. That was also true for the CVA's that I've cleaned. The only one I've had apart (CVA) the chamber was about 1/2 to 3/4" deep, before I changed that. Also, the one I had apart was drilled with a standard tip bit, so the bottom of the chamber will not be flat or square, but have the same angle as a drill bit (115 degrees?). Most guys don't like to take them apart because of the way they are put together. I got lucky that the old CVA came apart without destroying itself, from what I've learned here.
If I'm wrong here, hopefully someone with more experience (everybody?) will clue us both in.