bullet spinning like a top on ice

Story: -go to shoot ice in ditch -hear what sounds like a ricochet, nervous because it sounds like a tumbling bullet is going to land right on us at any second -ricochet sounds continues for 20-30 seconds -sounds more like a small electric motor whining -eventually quit cowering and follow sound -find this I bet it spun for a good minute at least before we found it We just caught the tail end of it on camera. It wasn’t even spinning fast enough to make the noise anymore. We got a lot of noisy spinning bullets, but this was the only one we actually caught on camera spinning like a top. Most landed on uneven ice&snow and tipped over before we’d find them, so we’d see them on their sides spinning instead.