With the damage to the receiver.. Tearing out the indexing Pin....
a single Grub-screw wouldn't stop the barrel movement with that pounding.
But maybe with a little modifications....
I went the route of Ernest Rowe... using 2 Grub-screws to secure the barrel for Tensioning....
But I also cut a groove for the grub-screw to sit in.
Also I can crank the Screws down without the fear of boogering the barrel extension up.
But even with these mods..... I am not sure it would hold up to a 5 lb sledge hammer!!
Stuart