Ingwe, been shooting with my .222 this past week with 50 gr. Vmax.
More than once I have noticed gophers hit but the bullet didn't expand.. Saw more than several go bouncing across the field, sometimes it was a miss,but often after hit the little rodent.. Any of this with the SX.? In the .223i have 40 gr Vmax. No problems there, super explosive. Hope you have a great shoot!
