I've been down this road. Mine was a screw. It pounds the top of the piston down making all of the ring grooves and landings tight thus mushrooming the piston top just slightly bigger. Mine was a SBC standard bore, but was just enough to crack the wall & introduce coolant into it. Sucks. My screw came out of the bottom of my quadrajet. Lock-tight is your friend.
Dropped an intake valve on a pass at the track once (not enough guide clearance, when I started leaning on the tuneup, it got hot and the valve hung open. Looking at the incrementals, it was on what would have been it's best ever pass when it happened) the debris went through the next four cylinders in the firing order, and the top of the piston in the first hole was so mushroomed, I had to drive it out with a hammer. The motor locked up and stopped turning, it was pretty close to the top of second gear, so it was probably turning about 6500 rpm when it broke, the motor coughed when the valve dropped, then caught for a second, then stopped turning. FWIW, also a dual plane intake.
Two cylinder walls were cracked, and there was water running out of the collectors when it towed into the pits. One head was destroyed (iron heads) the point of the story is yes, a piston can be swelled enough by beating on something like that to crack the bore. Been there, done that, got the t-shirt.
EDIT: sorry, my memory is not WHAT it used to be, I thought about this, one bore was cracked, the other had a deep gouge on the major thrust side. I had to sleeve two holes, that's what threw off my recollection.
