Picture a railroad spike, held vertically as if to be pounded into a railroad tie. Now picture a 14 pound bowling ball poised 35 feet above the spike, and then let drop straight down to hammer the spike down into the ground.
The energy m*g*h works out to about 600 joules, a typical energy for the .40 S&W bullet. On this picture it’s the third from the right. It’s also the caliber of the pistol I own.
Image courtesy Wikipedia
Now the damage the spike would do and the damage the bullet would do are two different things, but the comparison is not a terrible one. The energy of the bullet will be transfered to the body by exerting a force through a distance. While the speed and acceleration will be different, energy is the main quantity of interest and so the bowling ball provides a rather dramatic comparison as to just exactly how much you don’t want to be hit by a shot. The .40 S&W is probably the second most popular pistol cartridge after the 9mm round, which is the second from the right. Typical muzzle energies for the 9mm are around 480 J, or that bowling ball being dropped on the spike from 27 feet.
And you can go the other way up through the calibers to the .44 Magnum of Dirty Harry fame (second on left). Energy ranges widely for this one depending on the actual weight of the bullet, but 2000 J is perfectly plausible. That’s a 116 foot drop for the bowling ball onto the spike. Make my day indeed. It’s not the most powerful commercial pistol cartridge out there, but it’s the most powerful you’re likely to see in a gun for anything other than explicitly firing ridiculous specialty calibers.
Rifles? They’re several steps up, and while there’s many, many calibers out there I’ll only mention two. The .30-06 of WWII and hunting rifle fame is usually in the vicinity of 4000 J, or 230 feet worth of bowling ball drop. This is considerably more powerful than the ammunition currently used by US soldiers in their M16 rifles, as modern tactics generally prefer volume of fire over the strength of one particular powerful but bulky shot.
If you want a truly preposterous round, there’s the .50 BMG. Legal in most states (And why not? It won’t kill you any deader than a .30-06, each shot is about $4, and the guns that fire it are absurdly bulky.), it has a muzzle energy of an astonishing 13,000 J, or about 750 feet worth of bowling ball drop. But if you’re in an enemy APC it could ruin your whole day. Here’s it’s picture. It’s the big one. An M16 fires the second from the right.
Also from Wikipedia
The lesson to take away from all this? A Chevy Suburban at interstate speeds has something like a hundred times the kinetic energy of the .50 BMG. Like a car or truck, a bullet is a tool that is dangerous if not treated with respect. When you use them, be safe!
11 responses so far ↓
1 Uncle Al // Jul 28, 2008 at 10:18 am
1 J/s is a watt. 1 J/nsec is a billion watts. Impulse and area matter. Bullets are notable for quick delivery and rapid deceleration (hence hollow point semi-jackets). A rifle round can kill you while cleanly passing through via hydrostatic shock.
A diamond anvil cell deliverers big things wrapped in small packages. Modulus also matters. Don’t be there when reality stiffly chirps.
2 CCPhysicist // Jul 28, 2008 at 2:10 pm
The problem with your comparison is that many people will be imagining the momentum of the bowling ball, not its energy. Since p = sqrt(2mE), the bullet has MUCH less momentum than a bowling ball of the same energy.
Correcting for that factor of 530 in mass means the momentum is the same as if you dropped the bowling ball from a height of less than an inch. That explains why your handgun doesn’t knock you on your ass. It is momentum that determines the impulse, not energy.
The issue with the 50 cal is not the person in the enemy APC - although that is why my uncle always kept a high-power rifle with a 500 yard range handy just in case Russkies came down his suburban street (I am not joking). It is the policeman wearing lightweight body armor.
Anyway, number crunching only goes so far when trying to comprehend reality. Here is a link to a video of a WWI-era Vickers machine gun cutting down a tree.:
http://www.youtube.com/watch?v=Q2jdlfmaHuk
This gun fires a 0.303 round at 450 per minute.
If you liked that, check out this wonderful 24 min documentary of a kid tracking down and firing a Lewis Gun, which fired either 0.303 or 0.3006 ammunition at 550 rounds per minute:
http://www.youtube.com/watch?v=lgBm5HBXx3I
3 Paul Murray // Jul 28, 2008 at 8:15 pm
“A Chevy Suburban at interstate speeds has something like a hundred times the kinetic energy of the .50 BMG.”
True. And a freight train has even more. But they are useful for something besides killing people, so the implied “And it’s ok for people to drive chevys, right?” sort of misses the mark. If I’m carrying a can opener, it’s only fair to suppose that I intend to open a can.
Anyway: the problem with guns isn’t that they are more deadly than other deadly things (piledrivers, samurai swords, etc) - it’s that they are so easy to use.
4 Paul Murray // Jul 28, 2008 at 8:22 pm
Oh - and you don’t use a 50 cal on APCs. That’s what mines are for. 50 cal sniper rifles are for harassing fire from a km away. Sure, they might not hit anything accurately, but occasional 50 cal slugs coming from nowhere will slow down whatever you happen to be doing.
So the issue with 50 cals is not police with light body armour - you wouldn’t be able to swing the weapon around quick enough to hit them before they tasered or shot you. It’s shopping centres, movie theatres, and office blocks - particularly ones that have floors rented by government departments. Oh, and churches full of people with whom you disagree (eg: ones that let gays in). Any target-rich environment that you can fire into from a long way away.
5 Uncle Al // Jul 29, 2008 at 12:31 pm
A chemist, $1000; a handful of stuff…10,000 people are demented and unable to pee for 72 hrs. A burst bladder is a slowly horrible way to die. Society must be responsible for itself through global civic virtue and local vigilantism (because “some people just want to see the world burn”). “An armed society is a polite society,” Robert A. Heinlein.
Both sides of the badge are armed and remorseless. Only the unarmed middle gets chewed. A .30-06 round with a cadmium-plated Co-cemented tungsten carbide or uranium insert penetrates an inch of ductile armor plate. Super Bainite layered with toughened ceramic inserts is much better for the weight - are ya gonna ban pizza ovens?
6 Carl Brannen // Jul 29, 2008 at 1:42 pm
One of the first things I did when I became a math grad student and earned the handsome salary of $3500 per year was purchase a Ruger 10/22. I guess I should mention that I quit shooting around 10 years ago. A woman committed suicide at a gun range I was at. I suppose I will take it up again someday.
There are plenty of widely available rounds that I’m pretty sure would go right through standard body armor. Things designed to kill a large animal at 1000 yards have very high velocities at close range. There is a remarkably high percentage of the society that believes that hunters are unnecessary, but I think the death toll on the highways from driving into deer would exceed the number of firearm deaths per year.
7 Joel // Jul 30, 2008 at 3:31 pm
I’m not a math guy, but I wonder how accurate your facts are when you say “The .40 S&W is probably the second most popular pistol cartridge after the 9mm round”, somehow neglecting the .38 special, .357 magnum and .45ACP, all of which have been around much longer, and are much more popular than the relatively new .40sw round. I’m not saying any of your other statements are incorrect, but I have to look askance at your article as a whole if you manage to miss these very basic facts.
8 joel // Jul 31, 2008 at 9:22 am
Probably a fair comment for law enforcement, but not a general truth. The .40 is a fairly popular round for the average gun owner, but nowhere near as common as any of the other rounds on my short list.
9 kevin // Aug 1, 2008 at 12:35 pm
Paul, you’re dead wrong. A .50 cal IS used to fire at APC’s , trucks and fortified structures using API (armor piercing incediary) rounds which can penetrate approx 1″ armor plate. It is signigficantly useful at “soft” targets such as trucks, radar installations, mobile weapons system, etc. If you’d like proof of this, watch Future Weapons on Discovery Channel, or usually available on YouTube. As far as only good for harassing fire, you don’t know what you’re talking about. Barret rifles are being used by coalition forces in Iraq and Afghanistan as we speak. A Canadian sniper holds the record at a confirmed kill at (approx) 2345 meters (I can’t remember the exact distance). An anomoly, certainly, but a trained sniper can routinely hit a man sized target out to 2KM. This is also provable on the Future Weapons show. The US DoD named the Barret rifle, in its military form, as one of the greatest tools they’ve been given in the last 50 years.
10 Carl Brannen // Aug 1, 2008 at 5:16 pm
On the primary use of the .50, I agree with Paul. Record sniper distances and TV shows are not necessarily an indication of a weapon’s typical use. The vast majority of small caliber ammunition expended in war is used for harassing fire.
I don’t think I need to look up the .mil references to be sure of this. I would bet that the majority of .50 rounds are expended on arcs where the gunner doesn’t even have line of sight to the target.
I ran into an interesting article on the psychology of weapons. The subject is too complicated to abbreviate here, but the idea of most weapons (in actual use) is to give the enemy the idea that they could get hurt, rather than to actually hit them. Sure, if you can hit them that’s better, but you usually don’t have that option because most of the people on the other side are trying to survive.
In addition to hiding much better than deer, humans also shoot back, so it’s not safe to get near them.
11 kevin // Aug 2, 2008 at 9:53 am
You are correct, sir, that the majority of .50 is still used in the traditional method of “arcing fire” (grazing, defilade, or other means of traditional military fire). I’m not talking about what the majority of ammo consumption is, that’s immaterial to my point. Most beef sold is hamburger, doesn’t mean filet mignon doesn’t exist. Most TV shows are irrelevvant in the topic of firearms, but Futureweapons is dedicated to the cutting edge of military and LE technology, not what a director and special effects department can come up with. The host is a former SEAL sniper. I just wanted to raise the point that there is such a thing as accurate .50 fire, only in 10 round bursts through the use of a Barrett M107 and a trained sniper, and yes, they can take out an APC. Paul is right, we would prefer other means to take one out. Today the US forces will usually use air power, artillery, or as a last-ditch, shoulder-fired anti-tanks weapons like the SMAW. In a pinch, however, a .50 can definitely do the job.
I agree totally with the pschology issue, that’s why the cold war never got “hot” (yes, I know we had close calls). That’s also (partially) why crime rates have dropped in areas with a “Shall Issue” mentality towards concealed carry. Bad guys usually will target areas with minimal threat of meeting return fire before they take the risk of meeting armed resistance. Predators attack the weak target, that’s why schools and churches are often crime scenes.
And absolutely, your last statement is correct, that’s why DoD got a sniper rifle good for a 2000 yard range. It’s taken out mortar positions, barricaded snipers, and other very dangerous targets when the target had no idea they were in the crosshairs.
http://dsc.discovery.com/search/results.html?query=barrett+rifle&search.x=27&search.y=8
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