Ricochet is the best place on the internet to discuss the issues of the day, either through commenting on posts or writing your own for our active and dynamic community in a fully moderated environment. In addition, the Ricochet Audio Network offers over 50 original podcasts with new episodes released every day.
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
This problem reminds me of the occasional at sea weapons test, say using 5 inch white phosphorus air bursts as fireworks in celebration of a holiday or of nothing, or a rack of 500 pounders dropped within sight of the ship for a mid ocean air show for the crew.
It’s a big ocean, and it’s mostly empty.
Was that the original plan/intent? Deer hunting with a .22?
Yes. The rabbits were just in the way.
Shooting rabbits. Danny got a case of “buck fever.”
What do you mean? An African or European .223 bullet?
This answers the question, “Who needs more than a ten round magazine?”
Back in 1971 I was heading into the Nuristan area of Afghanistan on a climbing expedition. We were in Mercedes mini bus and passed a wedding celebration along the road. The men in the parade were holding AK-47s and shooting into the air. It was pretty scary wondering whether we would make it through the return barrage before we were well and safely passed them. We lucked out. I do wonder, periodically, how often the participants in such stupidity end up having to carry one of their number home for medical care.
Quick update for anyone who cares: my math was wrong, as explained here.
Which as a retire NASA engineer, I always did my calculations in metric, it has institutional egg faced precedence.
And even my correction is slightly misstated, in that acceleration is expressed in feet per second squared, not feet per second. Sheesh.
Returning home after a New Year’s Eve party in Natchez, MS about twenty years ago, I walked upstairs and found a .45 cal slug had gone through a thick tin scuttle-hole in the roof of my 1870’s two-story house, struck a framed photo on the landing, smashing the glass and frame, and coming to rest on the carpeted landing.
That same New Year’s Eve, or maybe the year after, I read that two persons walking in the French Quarter in N.O. were struck by falling bullets. One victim was shot in shoulder with serious complications, the other hit in the thigh with minor injury.
I’ve never stayed out past ten p.m. on 12/31 since.
Thank you, @flicker for doing the math!
I have long hated how people say “it comes down at the same speed it went up.” That is simple nonsense: the question is terminal velocity (speed at which wind resistance matches gravity). And then the question is one of the mass of the bullet itself. The total force number is not a lot.
Here is a BS-check: Hail
Is hail comparable to a falling bullet? Not directly. Hail is much less dense than a bullet, but its greater mass compensates. So hail can fall at 100 ft/second, and a bullet at 250 ft/s. But hail has much more mass.
We KNOW it hurts to be in a hail storm, and hail regularly deeply dents cars (but does not penetrate).
I think most bullets are designed to keep spinning for well over their projected range. It should still be spinning when it hits the ground from gravity drop if was fired around a degree or two angle. Most small bullets are direct fire, far below 30 deg elevation. I would guess it would tumble at some point if fired at 30 degrees but you would have to know it’s muzzle velocity and when spin is designed to slow down. If you knew that, it could be calculated. It would definitely tumble if fired vertically on the way down but I think it would be stable and spinning until it reached its height. I could be wrong on that last thought.
I agree the bullet probably won’t penetrate but the hail is way more brittle. If it had more velocity, it would probably splatter rather than bounce. A metal bullet is going to have different impact dynamics. I still think it’s going too slow to penetrate the metal roof. If you direct fire to the roof it could penetrate depending on the thickness of the steel. You have probably seen cars with bullet holes.
I have MADE cars have bullet holes. Spent an entire day doing a vehicle assault course, and we shot in, through, around cars – as well as through the windscreen from the inside. The last is a chaotic event, btw – you cannot predict where the bullet will go until you shoot enough to clear an opening.
We found that only the pillars and engine block stopped an AR round. Car doors provided no protection whatsoever for an AR, and only a few bits of the door affected a pistol round. Do NOT rely on a car door for bullet protection!
Very sound advice!!
Yes. Actually I was intending that the bullet was fired into the air, meaning no more than 30 degrees from vertical. The bullet comes to near a stop at apogee and reaccelerates on it’s way down. It is a good question, whether the rotational inertia on a bullet is less than the forward inertia. And I don’t know if it’s rotational drag coefficient near apogee is more or less than its forward drag.
Either way, two sources, BDB I think, and one on Quora, said that when fired upwards, rotation stops near apogee and after that the bullet tumbles on its return or else turns to fall butt-first. These two orientations give different drag coefficients.
And 30 degrees off vertical in which direction? If we want to get stupendously technical, we have to factor in if you have fired in the direction of the Earth’s spin or opposite it.
An enduring memory for me was firing steel jacketed 8mm Mauser bullets at a car wheel. One shot hit the — how do I describe this — the flat horizontal side of I guess 1/4-inch steel — essentially entering the steel at it’s edge — and the bullet displaced the steel to either side for a good two inches (I may be off here in measurements because it was so long ago) leaving a two-inch long tunnel through the steel without any deflection. I was impressed.
And at what latitude?
Photos of that would be VERY cool!
I thought of that and came back to mention it, but you beat me.
Also elevation…
And Earth’s gravity isn’t exactly the same everywhere either.
Why? Over the range and time involved, the Earth might as well be flat. Also, the atmosphere moves with the Earth.
You’ve got to shoot a lot farther than a .22 can before you have to start worrying about all that.
Into the wind.
But, yes, I thought of that, and Coriolis effect and wind speed. My guess is that tumbling would change point of impact more than earth’s rotation.
The point of this article is that the point of impact of these bullets is presupposed, and land on my house. :)
13°30′N
You know, you made me realize that while I understand the principles of spinning bullets, I know very little about how they despin. Normally they have plenty of spin for their range. I should look up artillery rounds. They spin, fired at high elevations, and have long ranges.
And do arching artillery rounds hit point first?