Re: 2" x 12" groups?
Also chech your Natural Point of Aim. Once your on target, all ready to pull the trigger, take your finger off the trigger and close your eyes for 5 seconds. see where you are on the target. If your off the bull, reposition and try again until your smack on the bull.
I doubt that your getting your but kicked that bad at 400 yards by a 5-7MPH wind. also, do you have a scope level? If your canted it can throw you badly, but usually you will have vertical stringing also.
Make sure that your not muscleing the gun, especially in your grip. you can be pretty sloppy and get away with alot, but haveing a super flexed grip will through you every time.
Also check your bi-pod. If its not secure you can have issues.
could you have someone else shoot it to compare?