A few years back I wanted to build a double rifle but wanted to do a practice run before I cut up a nice double. I found an old C.G. Bonehill hammer double and went to work.I never completed the practice rifle just got it to the point of having sigths so I could learn how to regulate a double.I chambered it in 45-120. After shooting approx. 125 rounds the only advantage I can see over the 45-70 is how cool those rounds look. With modern powder the 45-70 will give you all the power you want to subject a shotgun action to. But those long 45-120 cases will get your shooting buddies attention. Maybe I will dig out that old rifle and finish it.