7.62x39 vs. 5.56x45

[Cubo de Sangre]

I always assumed the AK round would be more lethal. This guy disagrees. If he's right then I guess I no longer want an AR in 7.62x39.

http://www.businessinsider.com/ak-47-wound-over-an-m4-2015-12

KE = ½ M (V1-V2)2

Breaking this equation down into its components, we have kinetic energy (KE) influenced by the mass (M) of the penetrating missile, as well as the velocity (V) of the missile.

This makes sense; it is logical that a heavier, faster missile will do more damage than a lighter, slower missile. What is important to understand is the relative influence that mass and velocity have on kinetic energy, as this is key to understanding why I'd rather be shot with an AK than with an M4.

You'll notice that the mass component of the KE equation is halved, whereas the velocity component is squared. For this reason, the velocity of the projectile has far more bearing on the energy that it delivers into the target than the mass.

 

[RerouteToRemain]

Hornady 75 gr tap

Hornady 5.56 62 gr tap barrier

Hornady 62 gr .223 tap barrier

Barns 50 gr TSX

Barns 50 gr TSX

Speer 64 gr



Nasty stuff.

 

[sub_thug]

There are other factors as well to why the 5.56 NATO round is more lethal than the 7.62X39. The rapid deceleration of the round in the body produces some pretty nasty effects.

The first, and most commonly talked about, is that the round actually starts to bounce around inside the body cavities. An entry wound could be in the chest, but the exit wound could be near the kidney. It could even be on the same side of the body as the entry wound, although this is highly unlikely. The slug can cut up the person as it makes its journey through the body, creating opportunities for massive internal hemorrhage, leading to the victim bleeding out.

The second is that the slug decelerates so quickly that it produces a small shock-wave in the body known as hydro-static shock. There is energy still moving forward around the slug, which produces this effect. That shock can lead to internal hemorrhage as well, which can also cause the victim to bleed out.

The 7.62 round operates as more of a hole-punch. It will hit the victim, and hit extremely hard, but is more likely to follow a predictable trajectory inside the body, potentially passing through to the other side.

I wouldn't want to be shot by either, but at close range, I think my odds for survival go up if I were to choose the 7.62X39.

 

[Gregolian]

I wouldn't want to be shot by either, but at close range, I think my odds for survival go up if I were to choose the 7.62X39.

I'm not a ballistic expert but... at close range your odds I think are the same or at that point the 7.62 catches up to the 5.56...... This is ignoring the human element of the person holding the gun IMO.


Also, I know in my state I CAN use a 7.62 for hunting but can't use a 5.56/.223 for hunting anything like deer or bigger.


Although I will say I agree on most everything else. The .223/5.56 is far more likely to "tumble" after entering the target whereas a 7.62 is like battering ram and just punches through.

 

[sub_thug]

I'm not a ballistic expert but... at close range your odds I think are the same or at that point the 7.62 catches up to the 5.56...... This is ignoring the human element of the person holding the gun IMO.


Also, I know in my state I CAN use a 7.62 for hunting but can't use a 5.56/.223 for hunting anything like deer or bigger.

You're factoring in the bullet's ability to actually knock you down. Like I said, the 7.62 will hit HARD.

I wouldn't want to follow that kind of blood trail anyways. Haha.

 

[Gregolian]

You're factoring in the bullet's ability to actually knock you down. Like I said, the 7.62 will hit HARD.

I wouldn't want to follow that kind of blood trail anyways. Haha.

Isn't "knock down" power a myth? Like, I'm a .45 fan but always laugh at the ".45 has knock-down power" argument that people use.

 

[Roaming East]

The 5.56 doesnt 'tumble'. It fragments rather violently. Upon impact at high speed, basically within 300 yards of the shot, the speed is high enough that the bullet jacket compresses and ruptures and fragments of the projectile yaw away from the wound channel fairly quickly. as far as 7.62 hitting 'hard'? between the standard FMJ loadings the various militaries of the world are using, you are talking the difference of about 100lbs...i.e. 1,500 ft'lbs v 1600 ft'lbs. insignificant enough for relative accuracy of the shooter to be more important than the individual rounds performance.

what the AK round IS markedly superior at, is the destruction of light cover. the heavier construction of the bullet tends to tear away concrete and brick far better than the 5.56 in any loading will do.

 

[Cubo de Sangre]

Isn't "knock down" power a myth? Like, I'm a .45 fan but always laugh at the ".45 has knock-down power" argument that people use.

I skipped out on physics, but doesn't it stand to reason? I shoot a round target on the ground with a 9mm and it moves a little. With the .40 it moves much further. Isn't that the "knock down power"?

 

[RerouteToRemain]

Isn't "knock down" power a myth? Like, I'm a .45 fan but always laugh at the ".45 has knock-down power" argument that people use.

Not really but it definitely isn't the entire story.

Bigger bullet doesn't equal more knock down power.

It is the combination of velocity, size, weight, energy transfer/expansion(if we are talking hp) and penetration(not too little or too far). Those things dictate what happens in the body.

If you have a bullet that is larger, gets more expansion and the same penetration, it had better knock down power. Shot placement is key but bullets that leave bigger cavities allow more leeway on shot placement.

A .45 +p (depending on the bullet weight) has better knock down power (the right combination of what is stated above) than 9mm +p. 9mm +p+ is better than standard .45. It's all depends on those things stated above.

10mm has better knock down than 45 +p...

 

[Gregolian]

Whenever I hear "knock down power" I get images of the person imagining what happens to people in bad action movies when they fly 10 feet after getting shot with a shotgun.

 

[Cubo de Sangre]

Flying through the air is what makes it look so bad ass.

 

[RerouteToRemain]

Whenever I hear "knock down power" I get images of the person imagining what happens to people in bad action movies when they fly 10 feet after getting shot with a shotgun.

Yeah a description would be better expansion and bigger wound cavity.

 

[My Spot]

Why do you want an AR in 7.62 anyhow?
A better comparison would be 5.45 vs. 5.56.

 

[Cubo de Sangre]

Why do you want an AR in 7.62 anyhow?

It sounded like fun. Bigger cheaper bullets causing more damage (or so I thought!).

 

[Roaming East]

my 10mm is smaller than .45 but is a superior round in every metric. so no 'bigger' doesnt automatically mean better.

 

[RerouteToRemain]

Just go 7.62x35 if you want 7.62.

 

[Roaming East]

or .300 black out

 

[Grrrr]

my 10mm is smaller than .45 but is a superior round in every metric. so no 'bigger' doesnt automatically mean better.

Huge 10mm fan myself

 

[MadSquabbles500]

Arent there stories of the 556 not fragmenting reliably, and or either fragmenting before it penetrates thereby not penetrating, or passing through completely then fragmenting, whilst leaving just a very small wound channel not enough to affect the bad guy?

Can 556 go through barriers like I dont know, wood studs or sheetrock walls, or even furniture?

 

[RerouteToRemain]

Arent there stories of the 556 not fragmenting reliably, and or either fragmenting before it penetrates thereby not penetrating, or passing through completely then fragmenting, whilst leaving just a very small wound channel not enough to affect the bad guy?

Can 556 go through barriers like I dont know, wood studs or sheetrock walls, or even furniture?

Yes to everything you said/asked. The fragmenting before would have to be a pretty thick/strong barrier.

This isn't ball ammo but here is a test with the 64 gr Speer.
Test starts at 1:35, he mislabeled the pop up in the video. He is shooting the AR at at 1:35 and the 9mm afterward.


Fmj through pork shoulder and wallboard