Las Vegas Shooting

I know very little about ballistics. Surely this man was simply raining down lead on the poor people below; no accuracy was needed? Would gravity help maintain velocity? I've heard that under pressure certain rounds simply enter the victim's body and simply ricochet around, doing maximum damage; does muzzle velocity matter much here?

Just thinking out loud.

I thought about it (it's been a while since I've thought of energy calculations), and the amount of energy from gravity would be minimal compared to the muzzle energy. A .223 Remington bullet might have a muzzle energy of maybe 1700 joules - just a number as there are a variety. If it weighs 3.6 grams (also variable) and came down from about 130 meters, I think the potential energy via gravity (with the gravitational constant as 9.8 N/kg) is the following:

0.0036kg x 130m x 9.8 N/kg = 4.59 joules.

So it's pretty obvious that the energy added by gravity isn't much relative to the energy from the charge.

Still - if it's got 10-25% of its original energy remaining, that's still about as powerful as many common handgun rounds at point blank.

Certainly he wasn't worried about accuracy from that distance using bump stocks. There were thousands of people there. Whether or not someone survives or not after getting hit (even with much reduced energy) may be a matter of chance - where it hits, if it penetrates, etc.
 
I thought about it (it's been a while since I've thought of energy calculations), and the amount of energy from gravity would be minimal compared to the muzzle energy. A .223 Remington bullet might have a muzzle energy of maybe 1700 joules - just a number as there are a variety. If it weighs 3.6 grams (also variable) and came down from about 130 meters, I think the potential energy via gravity (with the gravitational constant as 9.8 N/kg) is the following:

0.0036kg x 130m x 9.8 N/kg = 4.59 joules.

So it's pretty obvious that the energy added by gravity isn't much relative to the energy from the charge.

Still - if it's got 10-25% of its original energy remaining, that's still about as powerful as many common handgun rounds at point blank.

Certainly he wasn't worried about accuracy from that distance using bump stocks. There were thousands of people there. Whether or not someone survives or not after getting hit (even with much reduced energy) may be a matter of chance - where it hits, if it penetrates, etc.

See, that's what I love about the DIS. Ask a stupid question, get an educated answer :)
 
See, that's what I love about the DIS. Ask a stupid question, get an educated answer :)

I actually figured it for the earlier response, but thought against posting it. Of course there's a huge difference between the energy of a bullet falling over a 100 meters vs a car rolling 100 meters down a hill. That's tens of thousands of times heavier.

Of course at that distance it will slow down due to wind resistance. However, a lot of the calculations about effective range are about accuracy.
 
I thought about it (it's been a while since I've thought of energy calculations), and the amount of energy from gravity would be minimal compared to the muzzle energy. A .223 Remington bullet might have a muzzle energy of maybe 1700 joules - just a number as there are a variety. If it weighs 3.6 grams (also variable) and came down from about 130 meters, I think the potential energy via gravity (with the gravitational constant as 9.8 N/kg) is the following:

0.0036kg x 130m x 9.8 N/kg = 4.59 joules.

So it's pretty obvious that the energy added by gravity isn't much relative to the energy from the charge.

Still - if it's got 10-25% of its original energy remaining, that's still about as powerful as many common handgun rounds at point blank.

Certainly he wasn't worried about accuracy from that distance using bump stocks. There were thousands of people there. Whether or not someone survives or not after getting hit (even with much reduced energy) may be a matter of chance - where it hits, if it penetrates, etc.


A 55 grain Remington .223 load (pretty common load) has 1,281 ft*lbs of energy at the muzzle and 207 at 500 yards.

http://gundata.org/blog/post/223-ballistics-chart/

A typical 9mm handgun round is in excess of 300 ft*lbs of energy at the muzzle:

http://www.ballistics101.com/9mm.php
 


A 55 grain Remington .223 load (pretty common load) has 1,281 ft*lbs of energy at the muzzle and 207 at 500 yards.

http://gundata.org/blog/post/223-ballistics-chart/

A typical 9mm handgun round is in excess of 300 ft*lbs of energy at the muzzle:

http://www.ballistics101.com/9mm.php

I think I actually found that chart earlier, but it appears to show a round fired horizontally and how far it would drop over distance. That reduction in energy would make it similar to the muzzle energy of a .380 ACP. And of course the affect of gravity would be fairly small. Dropping a bullet from that window might injure someone, but it's highly unlikely to kill. I think another issue with these small bullets is that they tend to penetrate more easily with the same amount of energy.

Additionally - the dude put out a lot of lead. He was bound to hit several victims in the head, which is considerably more likely to cause death than to the torso. Certainly from that range it's a matter of reduced lethality, still lethal enough.
 
May as well have fired a rocket into the crowd. The man had a number of weapons, suggesting (I believe?) that many of them either over-heated or needed the time for reloading; he was out for firing the maximum number of rounds in the minimum amount of time possible.
 
May as well have fired a rocket into the crowd. The man had a number of weapons, suggesting (I believe?) that many of them either over-heated or needed the time for reloading; he was out for firing the maximum number of rounds in the minimum amount of time possible.

Of course they overheat when fired continuously like an automatic. However, rockets are hard to come by. He had several legally acquired weapons that were relatively easy to get and was able to switch between them.
 


Of course they overheat when fired continuously like an automatic. However, rockets are hard to come by. He had several legally acquired weapons that were relatively easy to get and was able to switch between them.

Yeah, I was being ironic with the rocket... of course RPGs are tougher to come by! May as well have a railgun!
 
Yeah, I was being ironic with the rocket... of course RPGs are tougher to come by! May as well have a railgun!

Heck - maybe a Romulan disruptor.

But obviously he amassed all these weapons because he intended to fire as quickly as possible, and you're right that after a while they will overheat. However, overheating doesn't necessarily render a weapon useless. It will damage it and perhaps decrease accuracy, but I'm not sure it's going to stop working. Someone who knows he's probably going to die isn't going to have too many concerns about that. The Virginia Tech shooting happened with the shooter amassing over a dozen loaded magazines as well as loose ammunition. He was able to reload quickly.
 

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