Let's look at some details. Assume your "monster gun" groups 6" at 75 yds. Allow 1" for unknow windage and loading factors. That would mean that you would have to have ZERO error in your visual aim and ZERO movement of the pistol inorder to ensure hitting a person, much less killing him.
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There is only one detail that counts. I didn't have any trouble putting the bullet where I needed it.
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Let's make that assumption. That means aiming at someon's belly button will put lead within three and one half inches from that spot. A good percentage of the time that's enough to damned near blow the target's spine out. If it doesn't he'll be staggered and in shock immediately. Forget it. He's dead.