I have a 30-30, .35, and .450 Marlin. You don't need a 45-70 for deer like you said but there is nothing wrong with it. Though you should know if you are going to be shooting hot loads in it the recoil is pretty hard. My .450 kicks harder than my buddies .375 H&H Magnum. So if you have problems with recoil I would stick to the factory 45-70 loads which are more than enough for almost anything that walks, and have a lighter recoil. Right now my buddy has a cut above his eye from shooting my .450. He shot it once and refuses to shoot it again.