Shoot! But Not Up in the Air

 

Question: What is the terminal velocity of a returning .223 bullet once shot into the air and coming back to the ground, and will it perforate a standard corrugated steel roof?  And what is the attitude of a bullet falling to earth?  Point first?  Point up as it was when it was fired?  Flat?

I’ve lived in this house for probably eight years, and it’s pretty standard to hear relatively distant gunfire on midnight entering the new year.  In years past living at a different house, this has been done from a high public park perched over the ocean, firing (one would think) out to sea in the direction the old Spanish cannons are pointed, and incidentally setting the steep grassy slope to the ocean on fire – never knew how – but pretty and without fireworks, and lasting a good hour or so.  Not much danger, except to the local cemetery.  Cemeteries, it seems, always get the choice locations and best views.

But for the past several years I’ve lived inland, and rapid gunfire on New Year’s was always in the distance.  This year new neighbors (there are a lot of them, including on the adjoining hill facing my house) have been getting less neighborly with their loud noises, setting off what I assume were M80s either singly or seemingly tied together and lit with a single fuse, pretty much testing them (or enjoying them) any time of the day or night.  They sound like gunfire and I figure this was why several police cars rolled up with sirens on a few days ago.

It’s hard for me to tell wrapped fireworks from semi-automatic gunfire, though tonight at half past twelve I did hear full-auto fire a quarter of a mile away, oddly, coming from the direction that I hear “The Star Spangled Banner” played every morning on the naval base.

As an aside, when I was in my teens, I wanted to live in a faraway land, in an exotic location, and in my imaginings, Truk (now called Chuuk) was pretty much as far as anyone could get, thousands of miles from anywhere.  And very interestingly, I recently realized that that’s just where circumstances have led me to live, in Oceania, near enough to Truk (or Chuuk) where Chuukese can find it in their interests to fly in on weekends and deliver reasonably fresh reef fish and rock lobsters to the local Sunday morning market.  And even today I’ve had a couple of Chuukese men and a boy cutting ten-foot-tall grass and jungle on my side lot.  Nice guys, Christian, and they speak English, though they are hard for me to understand and tend to do other things than what I employ them for, performing a different job than I wanted, but it seems to be turning out alright anyway.

Getting back to New Year’s, I was awakened a little before midnight by music blaring, engines revving, and explosions, and alerted with the sound of what seemed like a bullet or two hitting and clanging either along or through my roof.  And it got me thinking.

Spitzer-shaped bullets, in all the charts I’ve seen, travel in an arc, but never have I seen – but only was left to suppose – the attitude of the bullet in flight.  If a bullet is fired into the air at, say, a 30-degree angle, and the spin of the bullet continues throughout its flight, does the bullet keep its upward-pointing attitude?  Or does the spin reduce and allow the bullet to tumble?  And if tumbling, does free-fall cause the bullet to nose down at the end of its trajectory, perhaps as the result of aerodynamic drag?

In other words, am I more, or less, likely to have a hole in my roof?  Any answers would be welcome – other than that I just have to get up there and look for scratches or holes – which, deep down, I already know.

Thanks in advance,
Flicker

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  1. Stad Coolidge
    Stad
    @Stad

    Flicker: I’ve lived in this house for probably eight years, and it’s pretty standard to hear relatively distant gunfire on midnight entering the new year.

    Waaaaay back when we used to stay up until midnight on New Year’s Eve, I’d go outside and shoot one of my hypothetical guns.  However, I never shot into the air – always into the ground (avoiding the sprinkler pipes).  Why?  Because when you fire a gun into the air, the bullet will come down somewhere.  The last thing you want to happen is the bullet landing on someone’s head . . .

    • #1
  2. BDB Coolidge
    BDB
    @BDB

    Did some reading to bolster my biases — here you go:

    A spitzer fired vertically will tumble.  Fired at (oh say 30 above the horizon), it may remain aligned to its direction of flight, that is, pointing where it’s going.  Nominally, the vertical round will “stop” for a moment at the top of its arc (which is a line).  The inclined round will get to keep its aerodynamic-gyroscopic stability.  Nominally.  Bullets can tumble even at moderate ranges given the conditions.

    Even if the vertical round maintained its orientation upward just due to spin, it would tumble once it built up any speed falling backward.  Tumbling of course costs speed rapidly, so the vertical bullet is not a concern, while the inclined shot may be.  Just the same, the tin roof will probably protect you, especially from 223/5.56.  Even under ideal conditions, after 500 yds, they’re down to 20% energy.  Same for Russki 7.62, while NATO 7.62 (aka .308) is down to half energy.  Note that NATO 7.62 at half energy is hitting as hard as a 5.56 at point-blank BUT may tumble and is probably not hitting the roof square anyway.

    Typical pistol rounds may de disregarded given distance and a tin roof.

    • #2
  3. cdor Member
    cdor
    @cdor

    I do not know, Flicker, but shooting bullets randomly in the air is a very stupid thing to do. Happy New Year!

    • #3
  4. kedavis Coolidge
    kedavis
    @kedavis

    Stad (View Comment):

    Flicker: I’ve lived in this house for probably eight years, and it’s pretty standard to hear relatively distant gunfire on midnight entering the new year.

    Waaaaay back when we used to stay up until midnight on New Year’s Eve, I’d go outside and shoot one of my hypothetical guns. However, I never shot into the air – always into the ground (avoiding the sprinkler pipes). Why? Because when you fire a gun into the air, the bullet will come down somewhere. The last thing you want to happen is the bullet landing on someone’s head . . .

    Indeed.  People – including children – have been killed that way.  Some states have no-shooting-into-the-air laws named after them.

    • #4
  5. Randy Weivoda Moderator
    Randy Weivoda
    @RandyWeivoda

    Wait a minute.  Noted firearms expert Joe Biden has advised us that if someone is breaking into your house the smartest thing to do is fire a couple shotgun blasts up into the air to scare the robbers away.

    • #5
  6. Tex929rr Coolidge
    Tex929rr
    @Tex929rr

    I believe for a while patrol LEO’s in the Los Angeles metro area would all park under overpasses shortly before midnight until the bullets stopped coming down. 

    • #6
  7. Flicker Coolidge
    Flicker
    @Flicker

    BDB (View Comment):

    Did some reading to bolster my biases — here you go:

    A spitzer fired vertically will tumble. Fired at (oh say 30 above the horizon), it may remain aligned to its direction of flight, that is, pointing where it’s going. Nominally, the vertical round will “stop” for a moment at the top of its arc (which is a line). The inclined round will get to keep its aerodynamic-gyroscopic stability. Nominally. Bullets can tumble even at moderate ranges given the conditions.

    Even if the vertical round maintained its orientation upward just due to spin, it would tumble once it built up any speed falling backward. Tumbling of course costs speed rapidly, so the vertical bullet is not a concern, while the inclined shot may be. Just the same, the tin roof will probably protect you, especially from 223/5.56. Even under ideal conditions, after 500 yds, they’re down to 20% energy. Same for Russki 7.62, while NATO 7.62 (aka .308) is down to half energy. Note that NATO 7.62 at half energy is hitting as hard as a 5.56 at point-blank BUT may tumble and is probably not hitting the roof square anyway.

    Typical pistol rounds may de disregarded given distance and a tin roof.

    Thanks. This helps.  Just to be clear, I meant 30 degrees from vertical.  I don’t think many even dumb people would shoot at 45 degrees or lower (but some might).

    • #7
  8. Muleskinner, Weasel Wrangler Member
    Muleskinner, Weasel Wrangler
    @Muleskinner

    My brother-in-law has a travel trailer with a bullet-shaped (not round, more rectangular) hole in the roof, and a mark on the counter under the hole where the bullet came to rest. The story he got from the previous owner was that this happened at a National Park on the Fourth of July.

    • #8
  9. Flicker Coolidge
    Flicker
    @Flicker

    Randy Weivoda (View Comment):

    Wait a minute. Noted firearms expert Joe Biden has advised us that if someone is breaking into your house the smartest thing to do is fire a couple shotgun blasts up into the air to scare the robbers away.

    Bird shot’s alright.  Right?

    Interestingly, where I live, shotgun blank loads are more expensive than 12g 00 buckshot, on par with sabots.

    • #9
  10. BDB Coolidge
    BDB
    @BDB

    Flicker (View Comment):

    BDB (View Comment):

    Did some reading to bolster my biases — here you go:

    A spitzer fired vertically will tumble. Fired at (oh say 30 above the horizon), it may remain aligned to its direction of flight, that is, pointing where it’s going. Nominally, the vertical round will “stop” for a moment at the top of its arc (which is a line). The inclined round will get to keep its aerodynamic-gyroscopic stability. Nominally. Bullets can tumble even at moderate ranges given the conditions.

    Even if the vertical round maintained its orientation upward just due to spin, it would tumble once it built up any speed falling backward. Tumbling of course costs speed rapidly, so the vertical bullet is not a concern, while the inclined shot may be. Just the same, the tin roof will probably protect you, especially from 223/5.56. Even under ideal conditions, after 500 yds, they’re down to 20% energy. Same for Russki 7.62, while NATO 7.62 (aka .308) is down to half energy. Note that NATO 7.62 at half energy is hitting as hard as a 5.56 at point-blank BUT may tumble and is probably not hitting the roof square anyway.

    Typical pistol rounds may de disregarded given distance and a tin roof.

    Thanks. This helps. Just to be clear, I meant 30 degrees from vertical. I don’t think many even dumb people would shoot at 45 degrees or lower (but some might).

    Even better.

    • #10
  11. Doug Watt Moderator
    Doug Watt
    @DougWatt

    Tex929rr (View Comment):

    I believe for a while patrol LEO’s in the Los Angeles metro area would all park under overpasses shortly before midnight until the bullets stopped coming down.

    I have parked a police car on New Year’s Eve outside of a neighborhood that sounded like a firefight with three or more police cars.

    If you get an invite to attend a Saudi wedding, you might want to just send a gift and stay home.

    • #11
  12. kedavis Coolidge
    kedavis
    @kedavis

    BDB (View Comment):
    NATO 7.62 (aka .308)

    .308 NATO (7.62 x 51mm, as I recall), not to be confused with .308 Winchester (7.62 x 54mm).

    • #12
  13. Randy Weivoda Moderator
    Randy Weivoda
    @RandyWeivoda

    Doug Watt (View Comment):

    Tex929rr (View Comment):

    I believe for a while patrol LEO’s in the Los Angeles metro area would all park under overpasses shortly before midnight until the bullets stopped coming down.

    I have parked a police car on New Year’s Eve outside of a neighborhood that sounded like a firefight with three or more police cars.

    If you get an invite to attend a Saudi wedding, you might want to just send a gift and stay home.

    There have been times when a news report has come out about a wedding party being mistakenly attacked by the U.S. Army in Iraq or Afghanistan, and people wonder how such a terrible mistake could happen.

    • #13
  14. Flicker Coolidge
    Flicker
    @Flicker

    Doug Watt (View Comment):

    Tex929rr (View Comment):

    I believe for a while patrol LEO’s in the Los Angeles metro area would all park under overpasses shortly before midnight until the bullets stopped coming down.

    I have parked a police car on New Year’s Eve outside of a neighborhood that sounded like a firefight with three or more police cars.

    If you get an invite to attend a Saudi wedding, you might want to just send a gift and stay home.

    That’s a classic.

    • #14
  15. Tex929rr Coolidge
    Tex929rr
    @Tex929rr

    kedavis (View Comment):

    BDB (View Comment):
    NATO 7.62 (aka .308)

    .308 NATO (7.62 x 51mm, as I recall), not to be confused with .308 Winchester (7.62 x 54mm).

    I think 7.62 by 54 is also an eastern block round – Dragunov sniper rifle. Not the same as .308 (also , as you said, sometimes called 7.62 by 54).

    • #15
  16. Flicker Coolidge
    Flicker
    @Flicker

    Muleskinner, Weasel Wrangler (View Comment):

    My brother-in-law has a travel trailer with a bullet-shaped (not round, more rectangular) hole in the roof, and a mark on the counter under the hole where the bullet came to rest. The story he got from the previous owner was that this happened at a National Park on the Fourth of July.

    This is a little troubling.

    • #16
  17. BDB Coolidge
    BDB
    @BDB

    Flicker (View Comment):

    Muleskinner, Weasel Wrangler (View Comment):

    My brother-in-law has a travel trailer with a bullet-shaped (not round, more rectangular) hole in the roof, and a mark on the counter under the hole where the bullet came to rest. The story he got from the previous owner was that this happened at a National Park on the Fourth of July.

    This is a little troubling.

    Travel trailers are made of toilet paper.

    • #17
  18. Jim McConnell Member
    Jim McConnell
    @JimMcConnell

    A falling .223 bullet does not have enough mass to penetrate a metal roof.

    • #18
  19. Flicker Coolidge
    Flicker
    @Flicker

    BDB (View Comment):

    Flicker (View Comment):

    Muleskinner, Weasel Wrangler (View Comment):

    My brother-in-law has a travel trailer with a bullet-shaped (not round, more rectangular) hole in the roof, and a mark on the counter under the hole where the bullet came to rest. The story he got from the previous owner was that this happened at a National Park on the Fourth of July.

    This is a little troubling.

    Travel trailers are made of toilet paper.

    Yes, but to leave a mark on the counter after penetrating the roof seems that it would make quite a smack on the head.

    One other thing, I would love to have a recording of the 911 call I made (just to alert the police, who said they’d send around a patrol car).  I had gone outside just to see what I could see, and we couldn’t hear each other over the background gunfire, or whatever it was.  I had to stop talking for maybe ten or fifteen seconds because of a particularly close volley.

    Fun night.

    • #19
  20. Charlotte Member
    Charlotte
    @Charlotte

    I feel like you’re burying the lede here. You live in Micronesia??

    • #20
  21. Flicker Coolidge
    Flicker
    @Flicker

    Jim McConnell (View Comment):

    A falling .223 bullet does not have enough mass to penetrate a metal roof.

    Thanks.  That’s good to know.

    • #21
  22. Flicker Coolidge
    Flicker
    @Flicker

    Charlotte (View Comment):

    I feel like you’re burying the lede here. You live in Micronesia??

    Maybe!  :)

    • #22
  23. Flicker Coolidge
    Flicker
    @Flicker

    Oh, and for those who are interested, the terminal velocity for .223 is around 244 ft/sec and for 7.62 x 39 it’s 264.  But of course the larger bullet will have greater energy.

    And there’s this: “Based on hundreds of years of shooting at pigs, oxen, and human cadavers—not to mention ballistics gel and other objects—munitions experts estimate that a bullet must be traveling at least 200 feet per second (or 136 miles per hour) in order to break the skin, although one traveling as fast as 330 feet per second (225 mph) might bounce off your body under certain circumstances. The broad range depends on several factors, like how pointy the bullet is and which part of the body it strikes.”

    And there’s this from an anonymous source: “The terminal velocity would be affected by the weight of the bullet, the bullet’s aerodynamic stability and its composition (density). For a typical 150 grain, .30-cal, spire point, jacketed lead bullet that is fired upward it will stop spinning as it reaches apogee. As it falls, it can be expected to begin tumbling. That tumbling makes it very difficult to predict an exact number but you can expect the terminal velocity to be between 150 to 250 miles per hour. There are reported deaths that have resulted from people being struck by bullets falling back to earth.

    Cecil Adams reports a U.S. Army test that resulted in a terminal velocity of 300 feet per second (205 miles per hour) for a .30-cal bullet.”

    Nothing yet about steel rooves.

    • #23
  24. Henry Racette Moderator
    Henry Racette
    @HenryRacette

    [ Ignore everything here except the correction at the end. ]

    With all due respect to Jim (#18), I think the answer is a little less cut-and-dried than I originally believed. I’ve long been skeptical of the general lethality of falling small-arms projectiles, but I did a little calculating and now I’m less confident that my skepticism has been justified.

    Assuming I did the math right, and assuming a 65 grain .223 projectile that maintains ideal aerodynamic orientation throughout its flight and thus preserves a typical coefficient of drag of about 0.295, and using typical assumptions about air density, you get a projectile with a terminal velocity of about 310 feet per second.

    That’s slow by rifle projectile speeds, but hardly inconsequential. The kinetic energy of a 65 grain bullet moving at 310 feet per second is given by what is perhaps the only equation most of us remember from high school physics: kinetic-energy-equals-one-half-em-vee-squared.

    That falling 65 grain projectile weighs about 0.0093 pounds. 0.5 x 0.0093 x 310 x 310 gives us a kinetic energy at terminal velocity of about 445 foot-pounds.

    Again, in terms of the typical rifle, that isn’t a lot: only the lowly .22 and .17 caliber rounds produce less energy as they come out the muzzle. But it’s still two or three times the energy of the typical .22 caliber round fired at point-blank range.

    So I guess it depends on your tin roof. If a guy standing on the roof with a .22 plinking rifle points it straight down and pulls the trigger, are you confident that the bullet won’t make it to your pillow? Because that .223 round will be coming in with two or three times as much energy.

    Again, assuming I got the numbers right.


    CORRECTION:

    But I didn’t get the numbers right.

    The m in 1/2 m v^2 is mass, not weight. The bullet weight is 65 grains, which does indeed weigh about 0.0093 pounds. Unfortunately for me (but lucky for Flicker), that isn’t the bullet’s mass. The bullet’s mass is the weight divided by the gravitational acceleration here on Earth, which is about 32.2 ft/sec.

    So divide my resulting kinetic energy by 32.2, and we get a mere 14 foot-pounds. Nothing at all.

    Jim was almost certainly correct in #18, in that the bullet will not penetrate a metal roof: it lacks the kinetic energy to do so.

    As for my math… egg, meet face.

    • #24
  25. Flicker Coolidge
    Flicker
    @Flicker

    Henry Racette (View Comment):

    With all due respect to Jim (#18), I think the answer is a little less cut-and-dried than I originally believed. I’ve long been skeptical of the general lethality of falling small-arms projectiles, but I did a little calculating and now I’m less confident that my skepticism has been justified.

    Assuming I did the math right, and assuming a 65 grain .223 projectile that maintains ideal aerodynamic orientation throughout its flight and thus preserves a typical coefficient of drag of about 0.295, and using typical assumptions about air density, you get a projectile with a terminal velocity of about 310 feet per second.

    That’s slow by rifle projectile speeds, but hardly inconsequential. The kinetic energy of a 65 grain bullet moving at 310 feet per second is given by what is perhaps the only equation most of us remember from high school physics: kinetic-energy-equals-one-half-em-vee-squared.

    That falling 65 grain projectile weighs about 0.0093 pounds. 0.5 x 0.0093 x 310 x 310 gives us a kinetic energy at terminal velocity of about 445 foot-pounds.

    Again, in terms of the typical rifle, that isn’t a lot: only the lowly .22 and .17 caliber rounds produce less energy as they come out the muzzle. But it’s still two or three times the energy of the typical .22 caliber round fired at point-blank range.

    So I guess it depends on your tin roof. If a guy standing on the roof with a .22 plinking rifle points it straight down and pulls the trigger, are you confident that the bullet won’t make it to your pillow? Because that .223 round will be coming in with two or three times as much energy.

    Again, assuming I got the numbers right.

    Thanks, Henry.  And this is in line with other writings, with perhaps a higher terminal velocity.  This is understandable if the bullet changes attitude to point downward.  However one anonymous source says that bullet spin stops near apogee and this sort of makes sense as all (or almost all) of the original force applied to the bullet has been spent and spin produces rotational drag anyway.  If this is so, then the bullet would tumble.  Another source indicated that bullets tend to fall blunt end first, so there’s that.

    A bullet tumbling has a greater drag coefficient, so this would account for slower recorded terminal velocities, and and correspondingly lower energies.

    Still, I haven’t got the thickness of my steel roof, and I don’t have any excess pieces to look at, or to fire a .22 at, or even take a hammer and awl to.

    And 300 ft/sec can pierce the skin, but does not necessarily.  So I still think the answer could go either way, especially when taking into account the variabilities of the bullet’s attitude on impact into account.

    Thanks.

    • #25
  26. Sisyphus Member
    Sisyphus
    @Sisyphus

    It’s gonna smart.

    • #26
  27. BDB Coolidge
    BDB
    @BDB

    There’s stray voltage out there about how very much more lethal falling bullets strikes are than plain old being shot.  “Probably due to the increased likelihood of head strikes,” some ninny manufactures from whole cloth.  Sounds like a colossal case of selection bias.  If it bounces harmlessly off your hand, I bet the police and medical reporting apparati aren’t even spun up.

    • #27
  28. Flicker Coolidge
    Flicker
    @Flicker

    BDB (View Comment):

    There’s stray voltage out there about how very much more lethal falling bullets strikes are than plain old being shot. “Probably due to the increased likelihood of head strikes,” some ninny manufactures from whole cloth. Sounds like a colossal case of selection bias. If it bounces harmlessly off your hand, I bet the police and medical reporting apparati aren’t even spun up.

    I’m just trying to imagine what a bullet falling 20 stories in 1 second, what that would be like hitting flat and glancing off your head.  I imagine that that would do moderate damage.  At least a very bad laceration and perhaps a closed fracture, to perhaps even penetration.

    And then transferring that to the top of a thin steel helmet.  Probably at least a small dent, perhaps a biggish dent.

    • #28
  29. BDB Coolidge
    BDB
    @BDB

    Somebody described the energy of a 223 at terminal velocity to that of a brick falling about two feet.  Let us assume that the brick is poised so that it hits you with a corner and stays that way.  

    Definite ouch, could kill you if it hits in the right spot, and isn’t coming through a tin roof.  

    On average.  

    • #29
  30. Jim McConnell Member
    Jim McConnell
    @JimMcConnell

    Henry Racette (View Comment):

    With all due respect to Jim (#18), I think the answer is a little less cut-and-dried than I originally believed. I’ve long been skeptical of the general lethality of falling small-arms projectiles, but I did a little calculating and now I’m less confident that my skepticism has been justified.

    Assuming I did the math right, and assuming a 65 grain .223 projectile that maintains ideal aerodynamic orientation throughout its flight and thus preserves a typical coefficient of drag of about 0.295, and using typical assumptions about air density, you get a projectile with a terminal velocity of about 310 feet per second.

    That’s slow by rifle projectile speeds, but hardly inconsequential. The kinetic energy of a 65 grain bullet moving at 310 feet per second is given by what is perhaps the only equation most of us remember from high school physics: kinetic-energy-equals-one-half-em-vee-squared.

    That falling 65 grain projectile weighs about 0.0093 pounds. 0.5 x 0.0093 x 310 x 310 gives us a kinetic energy at terminal velocity of about 445 foot-pounds.

    Again, in terms of the typical rifle, that isn’t a lot: only the lowly .22 and .17 caliber rounds produce less energy as they come out the muzzle. But it’s still two or three times the energy of the typical .22 caliber round fired at point-blank range.

    So I guess it depends on your tin roof. If a guy standing on the roof with a .22 plinking rifle points it straight down and pulls the trigger, are you confident that the bullet won’t make it to your pillow? Because that .223 round will be coming in with two or three times as much energy.

    Again, assuming I got the numbers right.

    One needs to include the tensile strength of a typical steel roof in making the calculations?

    • #30
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