I've been using 6x48 screws for years with heavy recoilers, much stouter than a 9+ pound H&H, and haven't had one come loose yet. I've had some rifles d/t to 8x40, but that wasn't because I've had problems, I just figured during the build process it was cheap insurance.
If I understand you correctly you're saying that the screws stripped, not the receiver. If so, I'd treat those screws as suspect and have another go at it with the new ones. I'd secure them somewhere between farmer and gorilla tight. Use medium (blue) Loctite if you want, but I wouldn't use high-strength (red) on a 6x48 screw. If I misunderstand you and it's the receiver that stripped, then d/t to 8x40 is the easiest and most secure fix, unless you want to TIG the base in place...
