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Old March 25, 2005, 11:21 PM   #1
Full Metal Jacket
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Full Metal Jacket Theory

My theory on FMJ (full metal jacket) rounds is that could a FMJ 7.62x39mm or a 5.56x45mm bullet be less deadly then, say, a 9mm or .45ACP bullet since assuming the FMJ's all penetrate completely through, wouldn't the wider diameter pistol calibers be more likely to kill than the thinner diameter but much higher velocity rifle rounds? (sorry for that long sentence)

Simply put, a .45 hole is bigger than a .223 or a .308 one, so more blood would leak out of the target since all the rounds (lets assume) went through and through the target, dumping little to no energy.

Can anyone please prove this wrong?
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Old March 25, 2005, 11:26 PM   #2
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If the bullet stops within the target, then all its energy has been deposited. That's not to say that an FMJ can do as much soft tissue damage as an expanding bullet... but I'm not an expert in this field.

If you use Power Factor calcs, a .45ACP bullet has a lot more energy than a .223 (I'm assuming 950 fps/230 gr. and 2300 fps/55 gr. respectively.)
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Old March 26, 2005, 12:23 AM   #3
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Tissue damage is a function of velocity and diameter of projectile (and many other factors). A high-velocity but smaller caliber rifle bullet can easily damage more tissue and cause more blood loss than a larger, slower-moving bullet. Additionally, blood doesn't need to drain out of the hole to cause death; many people have died of internal bleeding.
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Old March 26, 2005, 01:48 AM   #4
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Energy can not be ignored.

There's more to terminal ballistics than bullet size and penetration. Just look at a piece of ballistic gelatin and tell me how the bullet can disrupt parts of the gelatin it doesn't touch if energy doesn't mean anything.
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Old March 26, 2005, 03:01 AM   #5
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then there's the type of tissue being disrupted

The crush and stretch cavities caused by the bullet passing through the tissue varies greatly depending on the tissue type. The brain, liver, kidneys, and other similar organs are not elastic, so the small fast moving bullet results in a "fracture" or shearing type of damage to these tissues directly relating to the speed of the projectile. I think it's called hydrostatic shock. Muscle and other elastic tissues will not react like liver and brain tissue. They will stretch with the temporary stretch cavity, whereas liver and similar non-elastic tissue will not. As stated by JohnKSa, the bullet doesn't need to make contact with the tissue to damage it in these types of organs.

Hypovolemic shock (passing out from loss of blood flow to the brain due do low blood bressure due to blood loss elsewhere in the body) as from a fractured liver can be rapid, or slow, depending upon the severity of the damage. The higher the velocity, the greater the shockwave. The liver in particular is a very vascular organ, along with the kidneys (being essentially filtering organs they get a lot of blood flow at any given moment), and as such, blood loss from the fracturing damage can be great.

Also, tests have shown that the 5.56 and similar fast-moving bullets can "yaw" or tumble in soft tissue widening the wound channel, they can also fracture at the crimping groove (cannelure?) and cause additional wound channels.

there are several good books on wound ballistics and others about why bullets perform the way they do, but the physics are above my head.

Suffice it to say that there are many factors besudes the size of the hole made that result in tissue damage.
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Old March 26, 2005, 03:50 AM   #6
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.45ACP bullet has a lot more energy than a .223

...that seems like a data-error:
a good .45 is about (all metric) 14grams at 230meters/sec = 500 Joule
a good .223 is about (all metric) 3,56grans at 988meter/sec=1740 Joule

The .223 has about three times the energy of the .45. You seem to overloock that kinetic energy is mass x speed x speed (=speed square) / 2
Therefore the bullet speed counts way more than its weight....
so no .45 has a chance of coming even close to the energy of a .223. The .45 would be en extremely hot load if it reached a third of the energy of a .223.
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Old March 26, 2005, 04:48 AM   #7
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Cheers people,

I've never seen a .45 exit the - what - wound, body, cavity, victim. A.223, all metal bullet, isn't even going to slow down - unless it hits a major bone deposit.

It's the expenditure (sp?) of energy that's causes the stopping power of the round. Yes, the "high speed" bullet can cause more damage than the slower, heavier round(due to hydrolic shock), but unless that bullet hit something that's going to stop it in the body, it's wasted energy. Yea, it might kill the guy behind him, but it really isn't going to stop the first "target".

Instead of "acceleration energy" you need to look at "deceleration energy" which looks at the stopping distance and the forces released into the "target".

My $.02

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Last edited by crashresidue; March 26, 2005 at 04:51 AM. Reason: spelling - of course
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Old March 26, 2005, 07:16 AM   #8
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I don't think 'energy' has that much to do with it.There are some new theories being investigated too. But the military 223 s tumble and even break in two pieces which do lots of damage. There are the secondary projectile [bullet hits a bone and bone fragments become projectiles] effects and other high velocity effects.So it's hard to compare the 223 with a 45 since the two have very different actions.
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Old March 26, 2005, 07:19 AM   #9
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I posted this on another thread, but will repeat it here. Many CQB Teams are using 5.56(.223) instead of 9mm or .45ACP SMG's because of the lack of OVERPENETRATION with the more powerfull rifle round. According to tests nad actual street results, 5.56 is less likely to overpenetrate and injure bystanders than 9mm.

At 2800-3000fps(closer to std vel than 2300) for .223, it has more energy than .44 mag, so How is it more powerful than .45ACP again?
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Old March 26, 2005, 11:00 AM   #10
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I also wouldent bet it would be all about over penetration. I would bet acuracy would have a big part of it to with the .223 being the better of the the cal. stated. Its my understandine handgun cal. SMG's have never been all that acurat.
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Old March 26, 2005, 11:17 AM   #11
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Its my understandine handgun cal. SMG's have never been all that acurat.
Unless they fire from the closed-bolt position. They are the minority.
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Old March 26, 2005, 12:51 PM   #12
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But the military 223 s tumble and even break in two pieces which do lots of damage.
All FMJ rifle rounds do exactly the same thing when entering a soft target. They try to assume a base-first position, since that's where the bullet's center of gravity lies. It doesn't matter whether you discuss .223, .308, or .45-70...given enough medium in which to flip base-first, they'll all do exactly one 180-degree rotation.

.223 has a tendency to fragment at the cannelure, and other light and fast loads like to break apart as well, but no rifle round "tumbles" in the target other than precisely one 180-degree flip from tip-first to base-first.
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Old March 26, 2005, 12:59 PM   #13
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Yes Marko, with the exception of places like Sweden and Switzerland ,where they make bullets that are desisned to do minimal damage !!!
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Old March 26, 2005, 01:12 PM   #14
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thanks for the responses, guys. I knew i was wrong, i just wanted someone to explain why. I think maybe some of you misinterpreted the question; i know a rifle bullet has more energy than a handgun bullet. I was just wondering if a .223 and a .45 bullet both overpenetrated a target, wouldn't the .45 be more lethal since its a bigger hole, and little energy is dumped in both cases. I guess the .223 would still have more energy than a .45 even when the energy is dumped.
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Old March 26, 2005, 02:08 PM   #15
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All I know is the DC sniper used a Bushmaster in .223 and he had no problem killing people nearly instantly with one shot.
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Old March 26, 2005, 03:12 PM   #16
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FMJ .223 bullets yaw and fragment IF the striking velocity is above 2700 fps. If the striking velocity is below 2700 fps this will not happen because the bullet will yaw, but not fragment.

As for .45ACP FMJ I have seen many men shot with it and it is a very effective bullet indeed.
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Old March 26, 2005, 04:19 PM   #17
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Hardball,

Saying that fragmentation occurs above 2700 fps seems to be a very broad generality. You need to look at the bullet weight and the rate of twist for the barrel.

The energy passing through a person has a tremendous effect. You cannot simply say that oh well, that .50 BMG round went clean through him so I guess the energy was wasted. What got wasted was the person hit by the .50 BMG.

As for the bullets tumbling, you are basing this on most rifle bullets being rear weight biased. Please talk to hunters and reassess your opinions. We are animals and weaker than most of the animals that are hunted. If bullets can pass through them without tumbling or turning around or breaking up, what makes you think it would happen in the human body. You need to take into account the gyroscopic force that rifling imparts into the bullet. Like a well thrown football, the spinning keeps the bullet very stable. If the bullet were to strike bone at an odd angle, it could deflect, but tumbling is not that common for higher powered rounds.
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Old March 26, 2005, 05:27 PM   #18
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Quote:
Power Factor calcs, a .45ACP bullet has a lot more energy than a .223
Power Factor and Energy are two different things. Kinetic energy is a measure of the potential of a moving object to do work and generally relates to the amount of damage that can potentially be caused by a bullet. Power Factor is a scaled version of momentum. Momementum is a measure of how hard it will be to stop a moving object and generally relates to penetration in a bullet.

You can not ignore either momentum or energy. Energy is what makes big stretch cavities and causes fragmentation and expansion. Momentum is what makes deep holes.
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Old March 26, 2005, 05:35 PM   #19
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Actually, momentum is what leads to penetration. What makes big holes is larger calibers and well designed hollow points. Arrows have lots of momentum due to all the weight but much lower speed compared to bullets. Arrows can penetrate many things that bullets can't.
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Old March 26, 2005, 06:10 PM   #20
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Quote:
Arrows can penetrate many things that bullets can't.
Examples, please.
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Old March 26, 2005, 06:28 PM   #21
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"Hardball,

Saying that fragmentation occurs above 2700 fps seems to be a very broad generality. You need to look at the bullet weight and the rate of twist for the barrel."

I'm speaking of .223 FMJ, not FMJ bullets in general. The velocity threshold is based on military analysis.
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Old March 26, 2005, 08:02 PM   #22
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Talking archery.

Arrows are not designed to expand or deposit energy into a target, it woud be a waste. You are talking about a whole 15 (fifteen) foot pounds of energy from a really fast bow. Arrows heads are designed to slice through and cut tissue, and energy that is transfered to the target negates this action.

Arrows do penetrate things, say like a plastic milk jug full of water quite easily, but that is because od a massive sectional density, and the lack of expansion and the propensity to yaw.

All Spire point bullets yaw, and some are designed to take advantage of this effect, like the russian 7.62 which yaws and flattens, making it achieve a more damaging terminal effect.

The 5.56 yaws as well, and does break at the cannelure (though I am not sure that the cannelure breaking was the original intent). Originally the 55 grain 5.56 was fired from a 1-14 twist barrel, giving the bullet enough stability to fly straight in the air, but caused it to destabilize quickly when it transitioned into another medium. Heavier bullets and tracer designs, as well as poor cold weather performance if the 1-14" twist barrels led to faster twist rates, like the 1-7" common in the military now.

the round nose bullets of FMJ .45acp and 9mm do not yaw as easily and, in that case, a bigger hole is desirable.
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Old March 26, 2005, 09:46 PM   #23
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Actually, momentum is what leads to penetration. What makes big holes is larger calibers and well designed hollow points
I think that's what I said about momentum and penetration--isn't it? When I said "deep holes" I was speaking of penetration.

As far as what makes BIG holes, I didn't address that. If you're talking just about the permanent wound channels, then bullet diameter and expansion play a part. However, it should be plain from looking at impacts in various mediums, or "bloodshot" meat in hunting, that there is damage beyond the actual permanent wound channel. That damage is largely the result of kinetic energy. Bullet expansion and fragmentation is also primarily a function of kinetic energy/velocity.

One of the comments about the 45/70, a relatively low velocity rifle round is that the bloodshot meat/temporary stretch cavity is remarkably small. That's just what should be expected based on the low velocity.

The extreme case of what temporary stretch cavities/kinetic energy can do is seen in varmint hunting when small animals are virtually "blown up" by the impact of a tiny, fast moving bullet. The bullet is clearly doing severe damage to parts of the animal that it never touches. That is not a function of momentum, expansion, bullet diameter or bullet design. It's a function of the velocity/energy of the bullet at impact.
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Old March 27, 2005, 01:30 PM   #24
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Quote:
Originally Posted by JohnKSa
The extreme case of what temporary stretch cavities/kinetic energy can do is seen in varmint hunting when small animals are virtually "blown up" by the impact of a tiny, fast moving bullet. The bullet is clearly doing severe damage to parts of the animal that it never touches. That is not a function of momentum, expansion, bullet diameter or bullet design. It's a function of the velocity/energy of the bullet at impact.
Varmits blow up because of the hydrostatic shock, which is a result of the velocity and energy of the round. Water does not expand. When you drop a rock in the water, you get ripples. The ripples is the hydrostatic shock in the body. When the liquid is contiained in an object that is contained such as a plastic jug or human body, a strong enough ripple (hydrostatic shock) will break the container or blow apart a prairie dog.

A .50 BMG will "cut" a person in half due to the hydrostatic force. A .50 caliber bullet moving at over 3000 feet/second has tremendous energy. When you take the weight of the bullet into account, you also have massive penetration. This is with FMJ bullets which should go perfectly straight through a person due to the sheer momentum the bullet carries.
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Old March 27, 2005, 03:58 PM   #25
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stephen426:

I'm still waiting on an answer for what arrows will penetrate that bullets won't!
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