I reloaded for a Colt New Service revolver I had in .44-40. A tip is to make haste slowly and use a four stage process rather than a three stage process as you would with a straight wall pistol case such as .44 Magnum or .45 Colt.
Three stage: Full length resize and decap. Flare case case and re-prime. Seat and crimp bullet into the charged case.
Four stage: Full length resize and decap. Flare case mouth and re-prime. Seat Bullet. Crimp bullet into charged case.
So on the four stage you seat all the bullets with the die adjusted to ONLY act as a seating die. When all have been done you then back off the seating stem and adjust the die to crimp only. With which you then crimp those rounds into which you've already seated their bullets.
This way you don't get collapsed shoulders as can occur with .44-40 if using a three stage process. If possible use a bullet with a crimp groove. Always only use a gentle crimp. Just enough, and only just enough, to turn the case mouth into the crimp groove. That's all that's needed.