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-   -   Can a Cross-Bow (etc.) Penetrate Kevlar Body Armor? (https://boards.straightdope.com/sdmb/showthread.php?t=80153)

tsunamisurfer 08-01-2001 07:32 PM

I recently read that the ability of longbows (and arrows) to penetrate medieval armor suits caused them to be obsolete very quickly.

Can an arrow propelled by a cross bow--or by a long bow--penetrate modern body armor? What about a knife wielded by a powerful opponent? A slug fired from a 12-gauge shotgun? A round fired from a big-game rifle?

Doc Nickel 08-01-2001 07:58 PM

In a word- Oh yeah.

A "bulletproof" vest works by being woven of very, very strong thread- variants of Kevlar, carbon fibers and "Beta" cloth, among others.

What this does is... well, the fibers don't break when struck by the bullet. This forces the projectile to deform, which spreads it's impact area out over a larger surface. The threads also tend to keep the projectile from penetrating.

However, a crossbow bolt typically has a nondeforming steel point, which can easily defeat a vest. A hunting type broadhead with two to four razor-sharp blades would have even less trouble.

Same goes for a knife- the edge can cut the fibers, and the point does not deform. It may well be more difficult to pierce a 'vest with a knife than a normal coat or jacket, but it's still possible.

As for a 12-guage slug, or other, "heavier" calibers, vests are rated for certain "threat levels". Meaning a certain vest is usually resistant up to and including, say, .357 Mag shooting a 125 grain bullet at up to about 1,200 fps.

A heavier bullet, or a lighter bullet traveling faster, or the same bullet in a nondeforming style (such as military "ball" ammo) have a better chance of defeating the armor.

In the case of the 12-guage slug, even if the vest were rated *near* that energy level, and perhaps had the optional "trauma plates" (typically, add-on sheets of titanium or even fiber-reinforced ceramics that can augment the threat level of the vest, or provide additional penetration protection) the sheer energy of the slug would cause major concussive internal injuries.

Tranquilis 08-01-2001 07:59 PM

As in medieval days, the answer is... It depends.

In medieval days, there were suits of armor called "proof" which had been shot at with crossbows (later, with firearms), and not been penetrated. Double "proof" armor had been shot twice. I've never heard of triple proof, but I suppose it happened. Proof armor was hideously expensive, and tended to be quite heavy. Crossbows were so effective in penetrating most armor that the Pope ruled it illegal for use against Christians.

Fast forward to today:
Modern body armor comes in a wide range of levels of effectiveness, but none are readily available that will stop a strong cross bow (or any strong bow, for that matter) unless the arrow hits a trauma plate. There was a Darwin Award nominee who was stabbed to death trying to demonstrate the knife resistant capabilities (poor, as it turns out) of body armor. I know of no body armor commercially available that'll stop a shotgun slug or a high-powered rifle. There are some bomb-resistnat suits or experemental suits that might do, however.

Doc Nickel 08-01-2001 08:02 PM

Forgot something:

As for mideval armor, it was predominantly iron, or what we'd call low-grade steel. It was typically pretty thin, else the suit would have weighed far too much.

Modern cars have thinner steel, but it's a far higher grade, with a much greater tensile strength. And even still, any reasonably able person can stab a dull screwdriver right through. The mideval stuff would have been worse than useless in the face of cross or long bows (little protection and slowed you down with it's weight.)

Tranquilis 08-01-2001 08:02 PM

D*mn. Left this out of my previous post.

starfish 08-01-2001 10:42 PM

http://www.nlectc.org/txtfiles/selectapp.html

For protection against rifles and shotgun slugs you need Level III. This is not usually soft body armor.

http://www.ordarm.com/
This company makes "soft" body armor for rifle and shotgun protection. It is a non-standard threat level. It is also over 1/2" thick.

Sam Stone 08-01-2001 11:12 PM

There are two ways to use Kevlar. One is in 'soft' armor, where the Kevlar is woven as threads, and another is 'hard' armor where the Kevlar material is soaked in resin and dried to make a composite structure that is very hard. These types of armor will stop a lot of things that the soft stuff won't, including knives and other sharp objects.

Whether it will stop a crossbow bolt or not depends on the specific armor and how powerful the crossbow is. A Crossbow bolt has a lot of mass, and is going very fast. That makes it a very tough thing to stop, and they can inflict a lot of damage.

The Hamster King 08-02-2001 10:18 AM

This is probably a good point to provide the link to the bear-proof suit.

http://thelonious.mit.edu/gman/

GregAtlanta 08-02-2001 10:57 AM

There was an incident a few years ago at a military school near here where the teenaged students were playing around with a bulletproof vest. They apparently thought it would stop anything. One kid put the vest on, and another kid charged him with a large knife. The knife went right through the vest and into his chest. The kid died.
-- Greg, Atlanta
(no reference or link, so feel free to be skeptical)

UncleBill 08-02-2001 11:08 AM

Greg, I knew the guy who had the knife. He was devasted by it, and it made the honorable mention in the Darwin's that year. He was in the Marine Corps Reserves.

Turbo Dog 08-02-2001 04:58 PM

Yes, a bladed object can penetrate body armor that is designed for bullets only. There are vests that have additional treatments to be stab resistant. That is what most prison guards wear. The certification is based on stopping an ice-pick driven with a certain amount of force (I forget the exact number).

As far as a 12 gauge slug, A level IV, which is the highest level that I'm aware of, will stop one shot, the same as with a 30-06 AP round. Those two have nearly identical levels of energy. A level IV is made by the addition of a ballistic steel trauma plate that is 1/2" thick. The ceramic ones are even thicker. As was mentioned though, there is no guarantee that you will survive the possible internal injuries.

tsunamisurfer 08-02-2001 08:38 PM

Quote:

Originally posted by Turbo Dog
As far as a 12 gauge slug, A level IV, which is the highest level that I'm aware of, will stop one shot, the same as with a 30-06 AP round. Those two have nearly identical levels of energy. A level IV is made by the addition of a ballistic steel trauma plate that is 1/2" thick. The ceramic ones are even thicker. As was mentioned though, there is no guarantee that you will survive the possible internal injuries.
Thanks for the info. I suppose I never fully appreciated the tremendous power of a 12-gauge shotgun.

Golden Child 08-03-2001 10:53 PM

I don't know what everyone else is think and I could be wrong but highly doubtful. Now when I was sent to the desert this past summer and it came time to get the good ol kevlar jacket out I was told by my commanding officer "Don't beto couragous because these aren't bulletproof" As I later found out Kevlar just stops pieces of mortar or metal that blows up near you....hmmmm go figure that one out. What about your head and everything else. Bulletproof vest are just simply mad up of stell plates of different kinds of thickness for different occasions.

Turbo Dog 08-04-2001 09:42 AM

Golden Child, that is because you weren't wearing ballistic body armor. You were wearing a flak jacket. Flak (shrapnel) will penetrate a bulletproof vest for the same reason a knife will. Bullets will penetrate a flak vest because the weave of the kevlar is different than in a ballistic vest. A flak vest is designed to basically grab the edges of irregular fragments. For most military situations, your odds of getting hit by frags rather than bullets is higher. Why not a vest that can do both? Cost and weight.

Cisco 08-04-2001 06:09 PM

While we're on the topic...I saw a thing on the History channel that said a Medieval longbow was the only thing that could penetrate bulletproof glass. But I thought some high powered rifles could also go through it? And what about modern longbows? What's the deal?

Turbo Dog 08-04-2001 07:45 PM

Bulletproof glass. It depends. Glass is rated similar to vests in that there is a specification on what it must be able to stop. There are, IIRC, 9 levels, the difference between the levels being the thickness of the glass. Level one has to stop 3 or 4 shots of 9mm. Highest level has to stop 5 7.62 rounds. So yes, an arrow shot from a longbow could realistically penetrate a lower level or two of bulletproof glass, but not the mid or upper levels. And it is by no means even close to being the only thing that will. Perhaps the only weapon of that time period that could, but that's about it. (Crossbows were, for the most part, very accurate, but very inefficient).

sewalk 08-04-2001 07:47 PM

There is really no such thing as bullet proof glass. There is bullet-resistant glass, which really isn't glass, but laminate plastic. There are bullets that will penetrate all but the thickest of these, specifically things like the .50 BMG, 14.5mm Russian, and a host of other much rarer loads that are what most people refer to as elephant guns.

As was said before, bolts and arrows are pretty good at going through armor because they are fast, heavy, and have steel points, just like armor-piercing bullets. Bullet-resistant glass is just another form of armor.

Crafter_Man 08-04-2001 07:49 PM

I've used Kevlar in some of my projects at work. To cut it, you must use a very special, esoteric tool called scissors. Any ol' pair will do.

Koxinga 08-04-2001 10:20 PM

What kind of body armor does the President wear? Would the Secret Service be more nervous about crosswbows than about rifles?

Not to go off on a tangent, but does the President wear a bulletproof vest all the time, or only when mingling with crowds or other particular occasions?

Mekhazzio 08-05-2001 12:24 AM

To put a bit of perspective on this:

Crossbow. A skilled operator could achieve, what, 12 shots a minute? That's probably being generous. Relatively short effective range (100 yards?)

Rifle. Standard assault rifles tend to fire around 600 rounds per minute or higher, in the hands of any user. With a moderate amount of skill, it can effectively match a crossbow's range easily -- with higher skill and the higher powered rifles, it can get up to two or three times that, and still easily penetrate any concealed personal armor a public figure might be wearing, if in fact, any do (probable, considering they'd be quite effective against the bigger threat of easily-concealed handguns)

The only advantages I could see for a crossbow is that it's unexpected, comparatively silent, no muzzle flash and can easily be made entirely out of composites (metal detectors) and does not involve gunpowder (dogs) Probably better from a covert perspective, good for James Bond, but when it comes to pure killing ability, a modern rifle far outclasses it.

sewalk 08-05-2001 01:03 AM

Quote:

Originally posted by Doghouse Reilly
What kind of body armor does the President wear?
It's called "secret service agents". As everybody knows by now, they actually train to interpose their bodies between the President and a potential threat and "catch the bullet". Body armor is not really very concealable. Police detectives often wear "overvests" that they can put on and remove quickly so they don't walk around all the time looking like they have something stuffed under their collars. I'd imagine that the POTUS doesn't wear body armor so as to avoid projecting a lack of confidence. If he does, in fact, wear protective armor, I'd imagine that it's of pretty limited value since it would have to be thin enough to be unnoticable to others. I've seen protective service training films where agents are trained to quickly throw an overvest around their principle if a threat suddenly appears, lending credence to the assumption that most Important Persons don't wear anything under their clothes.

Ross 08-05-2001 04:34 PM

:reads op:

Hmmm.

:gets up and walks to closet:

:takes something out and walks to window:

#TWANG#
#SCREAM#

:returns "thing" to closet:

:sits back at PC:

[PhilHartman] Yes, it can! [/PhilHartman]

Koxinga 08-05-2001 07:52 PM

Quote:

Originally posted by sewalk
Quote:

Originally posted by Doghouse Reilly
What kind of body armor does the President wear?
It's called "secret service agents". As everybody knows by now, they actually train to interpose their bodies between the President and a potential threat and "catch the bullet". Body armor is not really very concealable. Police detectives often wear "overvests" that they can put on and remove quickly so they don't walk around all the time looking like they have something stuffed under their collars. I'd imagine that the POTUS doesn't wear body armor so as to avoid projecting a lack of confidence. If he does, in fact, wear protective armor, I'd imagine that it's of pretty limited value since it would have to be thin enough to be unnoticable to others. I've seen protective service training films where agents are trained to quickly throw an overvest around their principle if a threat suddenly appears, lending credence to the assumption that most Important Persons don't wear anything under their clothes.

Maybe "body armor" wasn't the right term, but I do believe that presidents (at least sometimes) wear some kind of protection. I'm fairly certain that I read an interview with Ronald Reagan in which he said he would occasionally have to wear a bulletproof vest, and how much he disliked it.

Tranquilis 08-05-2001 08:36 PM

Here...
 
This ought to answer most questions. Warning: Requires Abode Acrobattm Reader, and is big (102 pages).


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