Hold the barrel up to a light and look through it to see if you can see any rust or corrosion. Befor this is done make sure it is clean and dry. Im not saying it is the barrel but it is a good place to start off. Was it cleaned good befor you put it away after last season? If so it should be fine. Did you check to make sure your scope mounts were snug, do you have removeable rings that put your scope back to zero after your removed it and put it back on, if it was removed?
A simple thing as just changing Primers would make a difference in where your groups were from last year. Let me know how the inside of your barrel looks and we'll go from there.
(BP)