Barrel appears to be walking out?

[G.T.]

Hi alexmg2420, and welcome to the forum parabellum.. This is a great place for info, and also a great place to enlist aid for your ailing Luger... First of all, don't shoot it anymore? You will run into pierced primers and other excessive headspace maladies......
It looks like an old revolver barrel to me, maybe it's all they had, when something is needed it's better than nothing?
If I was faced with a barreled receiver like yours, I would drill out the added retaining pin, and remove the barrel.. Then, I would run a tap into the receiver thread and straighten that out, and finally, re-barrel with a Luger barrel, new or used, of your choice.. If you would like to discuss the process that can make that happen, write me at: gctomeks@msn.com I am always willing to help new collectors and shooters, especially that are members of this forum.. we can work something out... Best to you, and again welcome, til...lat'r....GT