Hand loading in a single shot has its own little quirks. One of the good ones is that you can open the action and drop the projectile that you plan to use into the chamber. Let it drop until it hits the lands. Take your caliper and see just how far from the chamber end to the base of the bullet. Take a cleaning rod or short piece of rod, knock the bullet back out. Take the calipers and check the length of the bullet, add the two measurements, and then deduct the amount of jump to the lands that you want to try. That figure is your over all length for the loaded round. Double check your dummy round (Cause you need to make one) in the chamber and start working up your load. RECORD EVERYTHING! Nothing worse than finding a load that works great, taking a nap, and forgetting just what it was that worked so well. Cast bullets usually work best seated against the lands, jacketed varies. Some combinations want a long jump, some shorter. Most of the time, in the single shots, best accuracy is way below the max load. OOPS! The Rossi is a different deal. The majic marker is your friend there. You can also take a hacksaw and split the case mouth, deburr, and seat a bullet. Close the action and the bullet will seat to the max OAL against the lands. Remove carefully and check length. Hope this helps.