2 Kevlar Vests vs. a .308?

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Destructo is right. There is a video of Rich Davis of Second Chance body armor standing on one foot and getting shot in the chest with an FAL. He was fine, didn't fall down or anything.

Also I'm sure that must have been a level IV with a ceramic trauma plate. And that probably spreads out the impact some.

But still, I've never seen a 150-200 lbs. deer get knocked down by a .308.
 
If I remember correctly, the only vest which will defeat .308 is a Threat IV with a steel trauma plate. This vest is designed to stop 10 M2 .30 cal AP rounds ast 6 ft.
 
You guys crack me up with this energy dump BS! HA HA HA!

Level III is rated to stop 7.62NATO ball. Level IV is rated to stop .30-06 AP. Both are hard armor, e.g. ceramic plates. Soft body armor, even two vests wont stop 7.62NATO. Try it. I have shot soft body armor with rifle rounds (5.56mm, 7.62x39mm, 7.62NATO). I almost thought I missed because it zipped through so cleanly. the vest didn't even move. If it hits something that can stop it, like a Level III plate, then the energy is dispersed. The energy from the round is concentrated in one small spot on the vest, but the vest spreads out the energy across an area the size of the plate on the person. Only the plates on the military vests are rated to stop rifle rounds. And it depends on the plate you are issued (Level III or IV) if it will stop AP (black-tip). The soft portion is about a IIIA. Soldiers were shot in the plates by AK rounds in Somalia and their organs didn't magically turn to mush. HA HA HA!
 
I agree that if the vest has properly rated plates, then the energy will be dispersed on the 1st shot and will be survivable. The second shot is a different story.

What we were talking about (I believe) is two layers of unknown soft body armor. When in the context of two layers of soft body armor all of the above comment apply.

Kilgor
 
Correction to the LA story: the cops got AR-15s from a local gun shop, not a "street sweeper" (which is regulated by the ATF as a destructive device). One bandit killed himself, and another was killed when the cops finally aimed at his head.
 
I think nomix boy has it correct.

I do not believe 2 soft vests = 1 hard trama plate. I also don't believe a soft vest will block a 308. The reason?

Home done tests. .45ACP. 3.5 phonebooks, no problem. 308. 8 phonebooks, no problem. I ran out of phone books, but I'm sure up to 10 phonebooks would have been a clean hole. That's a lot for a soft vest to block. Even 2 soft vests.

I maintain the boy would have looked like ceramic pottery dropped from a 30 story building...

Albert
 
Out here in beverly hills the cops dont have to worry about bullet proof vests, no one here wants to pick up a big heavy gun that has grease and will get you dirty. If they want someone dead they just sue them till they have to move out of BH and go into the real world. But ive got a flak jacket and im more than willing to strap it on someone here and see if my Rem 700 PSS or AR 15 go through it... :D
 
Sorry boys, but Nomex Boy is right. Just look up the national reports of police slayings. I can't quote it, but if you find one that was shot in the torso with any of the high velocity round and he was wearing armor (soft level IIA, II, or IIIA) you will find the round passed through the front layer, the officer, and the back layer of armor. Tow layers won't do squat to stop high velocity ammo.

It takes a level III vest or better to stop high velocity ammo. That is what they're built for and thier not that uncommon, just expensive.

Still, I carry a second IIA vest (Older one that has been retired) in my trunk for those "this might be a firefight" type situations. I'd rather have two of these things on than 1 if those little speedy peices of lead start flying!
 
a "street sweeper" (which is regulated by the ATF as a destructive device). Buzz, its an "alley sweeper", that I called it. That's what we called the riot guns while I was in the service, back in trhe mid 60's. 12 gauge 20" barrel, no choke, 8 round mag, bayonet lug, and handguard (they were derived from the great M97 Winchester pump gun) and hell yes they can clean an alley RIGHT NOW! They are also legal.
 
Ossi's understanding is similar to mine: level 4 will stop .30-06 AP.

Southla1, as has been said, the Remington 870 from the gun shop in N Hollywood did not kill either robber.

I have fired a 2 3/4 slug into a Second Chance Level 2 at close range. Penetration did not occur. Vest was knocked approximately 2" into creosote-soaked wood. I'd say it would crack a sternum, but probably more survivable than a hole almost 1" through the body.
 
By wearing more than one vest, he may be on to something because of the amount of energy that can be dispersed by that amount of layering.

According to http://www.nlectc.org/txtfiles/BodyArmorStd/NIJSTD010103.html , a Level III (not IIIA) vest will stop a .308 and as already said, Level IV will stop a 30.06.

On of the reasons for trauma plates in vests is to increase the vest's strength over a somewhat delicate portion of the body, in front of and behind the heart. The trauma plate will dispersed the concentrated energy of a bullet into a larger area such as 5x9" or whatever the plates' sizes are.

People have been killed while wearing ballistic armor where the bullet did not penetrate the vest, but instead produced a concentrated blunt force trauma in a relatively small area. If over the heart, this may be enough to actually stop the heart.

In reading the catalog from Second Chance vests, many of the people wearing vests when shot did end up incapacitated, some knocked unconscious by the force of the impact.

An incoming round fired straight on will produce a cone of percussion (like what happens when BBs are shot at plate glass windows). Assuming the bullet does not penetrate and the person is not wearing a trauma plate, that cone of percussion can only spread out from the point of impact only so far before being transferred to the body. The thicker the protective medium, or in this case the additional layers, the cone of percussion will be able to expand more, hence the energy transferred to the body will be over a much greater area. As I recall, the Hollywood bank robbers understood this and also had layered their protective armor. As such, most of the rounds fired at the robbers did little to stop them since the bullets did not penetrate the vest and the multiple layers dispersed the energy enough to not have any sort of tremendous impact on their bodies.

As pointed out by yorec, two layers will not stop high velocity rounds if neither of the layers is rated for those rounds.

In regard to buzz_know on the Hollywodd bank robbers. One robber was reported to have committed suicide about the same time an officer managed to shoot the bandit in the back of the head. The other guy died not by being shot in the head, but from bleeding out from wounds suffered where the bullets did not pass through the vest, but entered the body where there as no vest. For example, both bandits had serious wounds in their arms where the bullets had entered through the opening of the armor sleeve, coming in through the hands/wrists.

One issue that might affect the officer wearing that much armor, aside from potential heat exhaustion, is one the Hollywood bandits had. With that much armor on, mobility is lessened considerably.
 
More info to muddy the water:
http://www.pinnaclearmor.com/new/ballistic_chart.html

No offense, but I must say that explanation in terms of F=Ma made me chuckle. It was sort of in the right direction, but not exactly good physics.

First off, due to the frictional loss of velocity, the bullet will have less kinetic energy when it arrives at the target than when it left the barrel. KE = (1/2) * m * v ^ 2.

Remember we’re not merely dealing with a force (during the firing of the rifle and the impact of the projectile), but we’re dealing with a force exerted over a distance. That is work. Work is defined as the dot product of the Force vector with the direction vector which can also be written as W = F * d * cos(angle_between_the_vectors). In our case, all of the forces are in the same direction as the movement, so W = F * d.

Now, work is also equivalent to the change in kinetic energy. We will assume that after the bullet impacts the vest, it no longer has any velocity left, and therefore no kinetic energy after impact. That allows us to equate the kinetic energy of the bullet with the work done in stopping the bullet. KE = F * d.

Let’s throw out the small amount of energy lost due to air friction (at close ranges) and say that the KE of the bullet at the muzzle equals the KE of the bullet at the vest.

Because the bullet is at rest before firing, the work done in accelerating the bullet out of the muzzle is equivalent to the KE of the bullet at the muzzle, which is equivalent to the work done by the vest to stop the bullet.

Now, let’s call F1 the force of the gun powder propelling the bullet. Let’s call d1 the distance over which F1 operates, which is the length of the barrel. F2 is the force the vest exerts to stop the bullet and d2 is the distance over which the vest moves while exerting that force.

Using our mathematical reasoning, F1 * d1 = F2 * d2. Now let’s play with some real numbers:

Let the rifle barrel be 21 inches long. Say that the combined movement of the vest deformation and the reward motion of the person being shot is 3 inches by the time the bullet comes to a complete stop.

21 / 3 = 7. Therefore, the force of the vest stopping the bullet is 7 times larger than the force exerted on the shoulder of the shooter.

Also keep in mind that the cross-sectional area of a .30 caliber bullet is Pi*(0.3)^2 = 0.283 square inches. The surface area of butt of the rifle is probably on the order of 10 square inches. This means that there is about 250 times the pressure exerted on the small area of the vest than there is on the shooter’s shoulder. (Pressure is force per unit area.)

Now you can start to see why shooting your M1A doesn’t wound your arm, but the flesh of the target you’re shooting at is damaged severely.

The vest must stop the bullet from entering into the body and must spread out the force of the bullet across as much area as possible. After seeing these numbers, it is entirely believable to me that a good vest could stop a .308..... But it will hurt like hell.

Now let’s look at “knock down”. It’s 3 AM and I don’t feel like getting into momentum, impulse (a force exerted over time), and integral calculus, so I’ll make this simple.

The force exerted on the shooter is spread out over a longer time than the force exerted on the target. So even though the target gets 7 times more force, that force is probably 7 times shorter in duration.

F = M * a. Therefore, a greater force leads to a greater acceleration (i.e. the body of the target is moved by the bullet’s impact). However, the time over which the acceleration operates is very short. How quick does a bullet stop when it hits a brick wall? Therefore, I would expect that a brief but strong force to jar the target’s body. It’s hard to say if this is enough to knock someone over, but I think that the force is so brief that it would be like a jaring sensation. It might have more of a stunning effect on the target. I think that if the target is “knocked” over, it is because of their own reflex reaction, not because they are pushed over from the force of the bullet. Perhaps if the target was in a position to be tipped over easily, it would be “knocked” over.

All of this typing and figuring makes me want to go shooting.... at paper targets or mannequins wearing Level III and IV vests.

good night.... errrr morning.
 
Wow, Q-Man! Nice to see a technical thinker at work - wish I had paid enough attention in class to spit those kind of formulas back out.

I followed most of it, but a couple of flys I spotted (I think) to dirty the ointment - most .308 rounds are pointed. Wouldn't this point and the angle of the point affect how well the penetration goes? I think a Spire Point would penetrate better than a SWC of equal cross sectional density. If you get what I mean?

Then throw in whether the tip actually strikes a strand of kevlar or between two as it impacts. And maybe count up the number of strands it has to breaks vs. the number it pushes apart to the breaking point.

Oh, and if I'm gonna get this nitpicky I'm sure the construction of the jacket (brass vs. moly coated, vs. lead) would comein to play too. Friction has to play a part, right?

Oh, and whether the flesh behind the vest is hard sternum or four inches of giving fat...

Would any of these things have a bearing on your equations? Lot's of little modifiers to think about. I think only the first, the pointed tip, would have much bearing and was my biggest question.

NOT finding fault with Q-Man here, just wishing I'd paid more attention in pysics class!!! Nice to see someone else was. I wanna go shoot a vest or two also!
 
A .308 FMJ can go through level II body armor at 1000 yards, from what I hear. At 50yards, I would not trust 2 vest unless they were level III:barf:
 
I don't have deep knowledge on kevlar against .308, but I had a chance to learn at the Russian Industrial Show in Washington, D.C. (5 years ago) about some products Russian defence industry was offering for sale. Anyway, one company presented bullet proof vests and helmets, heavily reinforced with titanium plates (helmet was 100% titanium). They claimed that
only use of hard materials (metals, ceramics, etc.) makes it possible to protect against full powered pointed .30 projectiles.
They supply these vests and helmets to ALPHA team. ALPHA team
is well known to use body armour capable of 100% protection against 7.62x39 and pointed FMJ rounds with similar level of energy, fired at point blank range. However I do not recall any discussion about .308, or 7.62x54R. I have a feeling that reasonably thick kevlar vest (or 2 vests similar to what this dude was wearing) will not protect against these calibers, capable of punching holes in 3/8" thick steel plates at 100 yards. It seems, logically speaking, that pointed FMJ bullets do have much better penetration against "cloth" type materials like kevlar.
 
Go to the website I posted above. Level III rating is defined by being able to stop a .308, fmj, of some velocity. The vest has the ability to stop .308 and level IV can stop more. Like with car crashes, however, the real concern is whether or not the person inside will still survive the blunt force trauma.
 
yorec, I'll admit it. I had to flip through a couple chapters of my college physics book to refresh my memory on the formulas.

Yes, the more pointed the tip, the more pressure that will be focused onto a smaller location on the vest. However, the tip must be one that will hold up to the pressure and not flatten. This is the principal behind the sharp pointed tungsten-carbide core of the armory piercing rounds.

Landing on or between a strand of Kevlar would also be a factor in whether the round might penetrate. The vest manufacturer would have to figure this into the type of weave of the material.

On a flexible vest, I think it the bullet struck over a bone, the bone would probably break--something’s got to give. All the force of the bullet would be focused at one point on the bone. The bone is likely to shorten the distance over which the bullet has to come to stop, and therefore, by the work equation, will cause a "spike" in the level of force the bullet is exerting. This makes it more likely that the bone will break. The breaking bone will, however, absorb a lot of energy from the bullet, and the bullet won't have much energy to continue moving.

If the bullet struck over a soft tissue area, the vest would deform into the soft tissue, probably sending a shockwave through the body that could possibly damage organs.

On a hard plate of armor, assuming there is not much deformation, the force of the impact is spread out over the surface area of the armor plate. There is less pressure at any one point and therefore less chance for bodily harm.

I have shot an AP tungsten-carbide round from my 30-06 through a 1/2 inch steel plate. I also know that there is a great difference in the types of metals and how they are made. I have heard of "rolled homogeneous steel" that will hold up a lot better than regular steel plate. I could see how ceramics and exotic metals could withstand an AP round. I sure wouldn't want to be the guinea pig behind the armor though.
 
Q-man, I don't think my F=Ma was all that bad, I understand the point about shooting at distance, but at something remotely close, like 5 feet, loss in energy and speed due to friction of air, probably not that big of a deal.

Now you have just brought up an interesting point, steel jacketed stuff. Armour piercing..

I don't believe that 2 Level II or IIA stuff will stop something with a steel jacket... or with a steel core rod like some of the GI armour piercing stuff.

Albert
 
Please note that Type III/IIIA are different. Type III is able to stop a .308 FMJ or lower. While type IIIA will only stop a 44 mag/9mm or lower.

I agree with the others that two Type II/IIA/IIIA will not stop a .308 FMJ. If someone would be kind to give me two IIIA body armor I would test it for them and post the results on the board.

For those who is confuse about the ALPHA team in Oris post. Spetsnaz ALPHA is what Oris meant. They are a special group of Spetsnaz that was under the control of the KGB in Soviet era. I think all their (Spetsnaz ALPHA) ranks was made up of officers. They are very good at what they did and that is killing and torture. They are now under the control of a Russian ministry which I forgotten the name.
 
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