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Old February 26, 2000, 07:41 PM   #1
HKMP5SD6
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I was wondering, which has more penentrating power? I know that the 5.56 is 45mm in length and the 7.62 39mm in length, does that mean the 5.56 has more charge? Does a smaller round mean higher velocity? And also, addressing the realisms of some of the SWAT FP shooters that I play on my computer, which round penetrates Level 3 body armor? Or do they both? Which round is overall better in combat?

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Old February 26, 2000, 10:34 PM   #2
Bud Helms
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HKMP5SD6,

The 5.56, AKA .223 Remington, is 44.7 mm long in the case. Bullet weights range from 45 grains up to 80 grains. The ballistics depend on the type of weapon the round is fired from, the barrel length and twist rate, the bullet type and weight, the powder type and charge weight. There are other smaller variables, but these are the major elements which determine the ballistic behavior of the cartridge.

The 7.62, AKA .308 Winchester, is 51.2 mm long in the case. Bullet weights range from 110 grains up to 180 grains. There are heavier .308 bullets, but practically speaking, 180 grs is about the upper limit for the .308 in commercial and military loadings. The same factors apply to ballistic behavior of this round. A reloading manual will explain all.

A 5.56 round may or may not be higher in velocity than a 7.62 round. It depends on the factors stated above. The 5.56 does not, nor does any other cartridge, have a fixed set of ballistic characteristics. There are too many variables at loading and in shooting. Each of the mentioned cartridges can be loaded with the right bullet and fired with sufficient velocity to impart adequate energy depending on the bullet weight to penetrate level III armor.

Get it? It's all variable. No pat answers. Every answer is a set of conditions. So, you can't say this cartridge will do that and that one will do this, until you get to the extremes of their capabilities.

The big differences are: the .223 shoots a little flatter, the .308 shoots a heavier bullet, so takes energy farther down range. They both kill, but the .308 can do it farther from the muzzle.

Both are accurate and that counts for a whole lot more than which one can penetrate level III body armor. One shot, One kill.



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Old February 26, 2000, 11:20 PM   #3
jcoyoung
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Comparing 5.56 (.223 Rem) and the 7.62x51 (.308 Win). The .308 will most likely have the most energy during any part of the bullets flight.

7.62x39 is a Russian round that is used in the AK47, SKS, and Ruger Mini-30.

Looking at my Lyman Reloading Handbook:
<LI>.223 Rem has an average muzzle velocity of about 3000 fps (using data for a 55gn bullet and max powder charge). Since energy is velocity X weight: Energy(.223)=165,000 ft-gn per sec
<LI>.308 Win has an average muzzle velocity of about 2800 fps (data for 150gn bullet and max powder charge). Energy(.308)=420,000 ft-gn per sec.
<LI>7.62x39 has an average muzzle velocity of about 2400 fps (using 125gn - max powder charge). Energy(7.62x39)= 300,000 ft-gn per sec.

Ignoring bullet diameter, bullet tumbling, bullet revolutions due to twist rate, etc. I would surmise that the 7.62x39 has superior energy to the .223. I'm no ballistics expert, so take these "numbers" with a grain of salt.

As for which round is better in combat, that all depends on the weapon, engagement distances, obstructions, background friendlies, etc. Depending on the situation, a subsonic suppressed 22LR may be the best choice for combat.


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[This message has been edited by jcoyoung (edited February 26, 2000).]
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Old February 27, 2000, 11:23 AM   #4
Bud Helms
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Ah, the 7.62x39. Well, then. Nevermind
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Old February 27, 2000, 01:13 PM   #5
Daniel Watters
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Actually, I believe that there is some confusion between Threat Level 3a and 3. Level 3a is rated to stop 9x19mm FMJ from a SMG and .44 Magnum SWC from a 6" barreled revolver. Level 3 is rated to stop conventional projectiles (FMJ, JSP, & JHP)fired from rifles, including the 5.56x45mm, 7.62x39mm, and 7.62x51mm. Level 4 is rated for rifle cartridges using AP projectiles.
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Old February 29, 2000, 05:13 PM   #6
TheOtherMikey
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The 5.56 (.223) is a high velocity cartridge which is really accurate out to over 500 yds with the heavier projectiles. These give the 5.56 more wind buffering capability than the 55 gr FMJ.

On the other hand, the 7.62 has charactistics similar to the 30-30 Winchester. At closer ranges (which an assault weapon is designed for) it is a formadable round but for accuracy at range it is a poor choice.

I have both and given the choice, I would choose the 5.56 hands down. Regards, Mikey.
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Old March 2, 2000, 05:24 PM   #7
Chad Young
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Actually the kinetic energy of a moving projectile at a contstant speed is:

KE = Kinetic Energy
M = Mass
V = Velocity

KE = .5 x [M x (V x V)]

This is usually expressed in foot pounds of energy in the English system or Joules in the metric system. In ranking muzzle energy of cartridges for an "Average" load, they rank, lowest to highest, as follows:

.223, 7.62x39, 7.62x51

As for penetration, I recommend reading the book, "The Ultimate Sniper." This book has a section where they test real-world penetration scenarios for multiple loads and calibers. Most of the time, a .308 comes out on top, but not always!

Hope this helps.

In a previous thread, someone posted a link to a site that allows you to punch in bullet weight and velocity and it will calculate muzzle energy for you.

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Old March 3, 2000, 01:56 PM   #8
Chad Young
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And that site would be:
http://www.realguns.com

Look under the Math section. A really handy site to have bookmarked!

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Old March 3, 2000, 08:22 PM   #9
jcoyoung
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Thank you for clearing that up Chad. I didn't really pay all that much attention in physics class . Sorry if I confused anyone.
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Old March 3, 2000, 10:18 PM   #10
beemerb
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I know all the charts and the rest but one added statement.A 223 isn't even legal for deer in many states.Would you bet your life on a round that can not be used to take deer?
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