The bullet is showing the same spin that it would have while in the air (i.e. along the same axis). I guess it bounced off the ice, landed again, and then maybe its heat melted the ice around it, which provided lubrication that let it spin for so long? I'm not a physics prof, though.
I'm just amazed that those guys weren't hit by ricochets - that bullet ended up behind them, just off to the left, after all.
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