Greetings My Good Supremo -
Unfortunately, the exact dimensions of the C&B Colt replicas are as variable as the makers. The Original Colt patents indicate a straight cylindrical chamber with a hemispherical bottom ( by the nipple) but the replicas have a mild taper to them. When I can get to my revolvers, I can try to make a wax casting for you , but it will vary by manufacturer and year, and I expect it will also vary with the inevitable wear on the tooling....
yhs
prof marvel