Crimp length refers to the distance from the mouth of the case to the end of the cylinder. Veral's catalog states - " to determine the proper nose length (crimp length), hold a CRIMPED empty case firmly in the cylinder, then, with the depth guage on a caliper, measure inside the cylinder throat from the front down to the crimp. Our closest offering Under the measurement is the correct nose length for your gun." His offerings are .35, .40, .45, and .50 for revolvers larger than 41 caliber. My two S&W 29's took a .45, it's a simple job to measure and determine the correct nose length.
Good Luck