If what you want to do is shoot targets and your set on a Sharps then don't get a carbine in 45-70. Way to brutal instead get a heavier model. Mine weighs 14lbs and handles the recoil nicely.

With the Sharps I can shoot a 80-100 round string and my shoulder is hardly sore the next day. Tryed that once with my 8 lb Marlin 1895 CB my shoulder was brused and sore for a week.

If you want to hunt then as plains99 pointed out a ruger #1 is a far better choice. Much more user friendly and you can use heavier loads. You can also add a muzzel break and recoil compensater to stock to help manage recoil.

Also if down the road you decide you want something bigger and more powerful the Ruger can be rechambered.

Last but not least the Ruger will be about 1/3 the price of the Sharps and you probably won't have to wait for it.