While I was sighting in my new .300 WSM Winchester Model 70 yesterday, I had something happen that I haven't had before.

I was taking a lot of time between shots, and cleaning after each one and letting it cool. when I finally got it where I wanted it, I went ahead and fired a 3 shot group. It strung the 3 shots out righht to left. 1st shot right no the money, 2nd shot about 1 inch left, 3rd shot about 3/4" left. I let the gun cool down and cleaned it again. Fired second group, smae exact thing. My vertical point of impact is staying right whre I want it, but it's stringing right to left.

The gun is a Model 70 Laminate Stock .300WSM shooting 180 Grain Winchester Factory Ammo (Plain Silver Box)

Any ideas or potential fixes ?