You are the first person I have heard of that has had this issue but next time I am in my local gun shop (they sell a ton of these Browning X-Bolt rifles) I will ask them. So you were lucky enough to only strip the screw then? Have you found a solution (ie a smaller screw) yet?
I know you mentioned above that you recently bought the x-bolt but did you have any ammo through the gun at all?