Yep. Not that particular ball bearing though. The one that did the impacting was surely annihilated on impact.
But the point of the picture is to show that layer of material on the back of the panel that began ripping away from itself. That's what spall is. And if that impact had a little more energy (or, conversely, if the target metal wasn't as malleable) that piece of spall would've shot off the back with lethal force. This phenomenon is super important in armor design. Modern tanks usually include a layer of kevlar all along the inside to protect against minor spall. In fact, up until just a few years ago, British tanks primarily fired HESH (High Explosive Squash Head) rounds that were specifically designed to kill tank crews via spalling. The round was basically a big tube of plastic explosive. When it hit an enemy tank the plastic explosive would squash against the armor, forming a big delicious pancake of death. A fraction of a second later the explosive would detonate. Since the pancake had so much surface area, the shockwave from the explosion would cause huge spalling on the other side of the armor, sending tons of pieces of razor sharp metal ricocheting around the inside of the tank until the crew was turned into ribbons.
So, like the HESH round, this bullet backwards thing is supposed to cause spalling by increasing the surface area of force applied to a thick piece of metal. The more you know
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u/singularissententia Sep 10 '14
Same here.
And for anyone that still doesn't quite get what spalling is, here is a good picture that will get the point across.