You do realise that your friend has applied an after-market device that is not warrantied nor allowed for in the design parameter of the original equipment manufacturer.
If you think this is anything like a warranty issue then you may suggest to your friend that he should take his nice new car for a spin across a lake, then see how quick the car manufacturer replaces his non-floating vehicle.
Short answer: suck it up princess and take responsibility for your stuff-ups.
My problem with that is if the relatively gentle recoil of a .308 did that while sitting on a bipod, I certainly wouldn't have much faith in the integrity of the stock/sling stud to hold my rifle on my shoulder using a sling and hold up to any serious josteling. And what if a guy wanted to shoot supported with the sling? That puts a fair bit of pressure on that stud. I'd call it a manufacturer defect for sure.
