I am shooting my 223 20" axis today at the range and I see through my scope that when I put pressure on the trigger that my crosshair hairs move down as I apply pressure and up as I release the pressure.

What would cause this?

I was trying my hardest to have a good grip and a good cheek weld but it was obvious that the movement was a direct effect of the trigger pressure.

I can't imagine it was the stock flexing. I did try squeezing the trigger just with my opposite hand using the trigger and trigger guard this would cause zero movement.