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Comment by bradleyland | Hacker News Reader

I was at a New Year's Eve party one time when a bullet pierced the roof of an awning covering the back porch. The impact was loud enough that we heard it over the music and cheering ringing in the new year.

The roof was constructed of corrugated aluminum. Not the strongest stuff in the world, but the bullet passed through two sheets of this material on its way in. We estimated the entry angle at around 40-45° by looking upward through the holes, aligning the light that shined through them (the following day).

Having seen it first hand, I would dispute the assertion that shooting in to the air at a high angle isn't particularly dangerous.

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Did you recover the bullet? Measurements of the bullet would hint at the cartridge used, which would let us calculate how and where the round was fired.

There are certainly cartridges in production that carry dramatically more kinetic energy than the example I used, but the more powerful cartridges tend to be more rare.

Note that as velocity bleeds off the trajectory degrades faster and faster, resembling an upside down exponential curve. The angle of impact is much greater than the angle at which the round was fired; more so as distance increases.

We couldn't find it. It entered the roof near the edge, continued through the screen, and in to the ground outdoors. We did a lot of digging around, but ultimately were unable to recover the round.

The holes in the aluminum roof were round (ruling out a tumbling rifle round) and were definitely larger than .22 caliber. Most gun discharges on occasions like New Year's are handguns, so it could have been any number of handgun rounds in the .35-.40 caliber range. It wasn't large enough to have been 45ACP or .44 Mag. It could have been a .30 caliber rifle round, but given the estimated angle of entry, I would have assumed it would tumble by then. To leave such a clean entry/exit hole would seem unlikely for a tumbling rifle round.

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