Anything much over 18 grains in a .36 will beat it to death.
18-20 gr is about all the Spiller&Burr chambers will hold they don't hold as much powder as the Colt chambers. The solid frame of the Spiller & Burr is a good deal less subject to damage than the open frame of the Brass framed Confederate Colt copies.
The S&B frame is more massive at the front than the remington frame, its squared off. The original plan called for the more streamlined top strap but to simplify production they left the frame blocky and thick at the front.