Cast iron ring breakage was pretty common and one of the reasons ring manufacturers went to "ductile iron" and most recently steel for top rings as they see the high cylinder pressures. Second ring breakage is a bit less common but will happen with detonation over time. Ring ridge is a tell tale indicator of a cast iron top ring . Barrel faced, moly rings are MUCH easier on cylinder walls and ring ridge is not as common.
The pistons usually suffer in the ring grooves when a ring breaks. They tend to "wallow" out , getting too wide to properly seal if reused. They also crack or break off if the detonation is severe enough.
Randy
