Every serious, yes serious, prepper/gun enthusiast should have a used 50 cal bmg barrel in their inventory along with a hard copy of the plans to build a bolt action 50 cal rifle. Having a garage machine shop and the supplies to build homebrew weapons would be a plus.
While I am on this subject. Hard copies of all the dimensioned part(s) drawings for your favorite weapons is a good idea also.
And yes as noted the welding on the OP gun leaves something to be desired.
I have thought about what it would take to build a .50 cal from a barrel for a while, so the way these people did it was of interest to me.
Production of a .50 cal barrel from stock, now that takes some serious work. Could be done, but not a simple homebrew project!