Look into actual "Pellet" guns. The hole is the precise hourglass shape of a pellet.Not saying for sure that's what caused the problem, but that's what a pellet looks like from the side.
It's about the same look if you look at a pellet from the side but that's not it. Anderspud nailed it. The shape of the damage is an exact match to the flutes of a drill bit.
I have just removed several posts from this thread made by 2 members - and both of you know who you are. So here's the deal, you will both stop the nonsense and follow the forum rules, or you will both suffer the consequences. And yes, I will be watching, and not just in this thread.
The more I think about it, the more sense that makes. We'll never know, of course, but it's quite plausible. I hate not knowing.
Your comment would be less amusing if it weren't so close to the truth. I'm already wondering how hard you'd have to pound a bit to make that impression in one swing.