I had a Contender with 14inch 45./70 also. I shot Garrett's 500 something grain rounds. It had alot of recoil and limited range. I switched to the Encore frame and had a Custom 18 1/2 inch .300 Win Mag barrel made with a muzzle brake. I put a scope and bi-pod on it. The weight of the gun, scope, and bi-pod is 12 lbs. I shoot Federal High Energy 200 grain to make up for a few inches less barrel than a rifle. With the weight of the gun and muzzle brake the hardly moves when shot. There is a hell of a muzzle blast, but the gun jumps up just a few inches and doesn't come back at you at all. I repeat the muzzle brake isn't optional! With out the muzzle brake this gun will jump, buck, and pound you!
I have shot deer and elk with this gun. The gun will shoot as far as you are good at holding it to. I have shot it for fun on paper out to 600 yds. to test my ability to hold still and trigger pull. The .300 win mag and the pistol will do it, it's up to you to hold it that still.
One last thing, my Contender has 3 times better trigger than my Encore. The Encore needs trigger help straight from the factory. It has alot of creep and is alot heavier pull.