Many of you know that many unique weapons can be gotten more than once. The Cram Opener, Lucky, ect., and the Mysterious Magnum is included in this list as well.

How? Well, supposedly, you can pick his pocket for it before and after the quest he is involved in. I've already taken his ammunition (with a sneak skill of only 44) but even with a damn stealthboy I can't grab it from his warm, still-living hands!

So, do I still need to give him another weapon and ammunition for it? If I do, would a 9mm be enough? What the cheapest, easiest-to-find weapon (with the lowest DAM possible) that can be used?

Note: My companions were with me when I tried this, I was [HIDDEN], it was dark, I was using a stealthboy, and I attempted both when he was sitting on the tree stump and when he was sleeping.

I think you glitched it.

After you do the quest he gives you the weapon.
Perhaps when you took the ammo it glitched it into him not giving you anything.

I didn't care about his quest so trying to pick pocket him to get it he turned hostile so I killed him and got it.

If you care about finishing the quest, then I got nothing for ya

I do care about the quest, but it says on the Wiki that this is a way to get two of them.

You could just end his life when you meet him next to the billboard. Thats what I did to get the gun. Then I was reading through my game guide and saw that there was a quest related to him. So, I reloaded the save before I killed him.

Take the ammo for his gun, then reverse-pickpocket a different gun and a couple rounds for it into his inventory. He'll equip the new gun, allowing you to swipe the Magnum.

If the weapon is showing up in his inventory the only thing you can do is keep trying OR do the associated quest and pass the barter check so he gives it to you. Assuming you have comprehension no skill points should be required. The magazine adds +20, a merchants outfit adds 10, and the four skill book add 16 which is a total of 46.