I just use 3' dowels and a razor for my break action rifles. Insert bullet and hold in place with a short dowel. Slide the 3' dowel in the muzzle until it makes contact and slide the razor across the muzzle making a small cut. Remove bullet, close action, and slide the dowel in to the breech face and make another mark. You have to then subtract headspace because you don't want the bullet kissing and shoving the case back against the face. These rifles are not exactly like loading for bolt rifles, but quite simple when you get the hang of it. To simplify, I just don't load to kiss lands. Buy a set of shim gauges to check your headspace when FL sizing if you have enough barel to frame gap.
Read Mike Bellm's website to clarify some of the above.
