Have you changed ammo or is this a new batch and what brand? The 17 HMR couldn't hold enough powder to damage a Contender barrel or hurt a frame. If the original frame and barrel are still together then it is most likely an ammo issue. I've had similiar issues with Hornady ammo in other calibers. I would get the lot number off the box and call the manufacturer and see if they have had any problems. The ammo could also be the cause of the accuracy issues although the sight could have been bumped but I would get the case cracking issue taken care of first.