Comparing 7.62x39 and 7.62x51 both in FMJ

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my762buzz

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If both rounds were to be used in FMJ ONLY, would there be a terminal
performance difference in a soft target such as a human in a battle field situation? Or would there just be identical 30 caliber holes in either case?
Will the higher speed of the 7.62x51 FMJ shatter bones and disrupt soft tissue more than the 7.62x39?
 
The vast majority of 7.62x54r is either hard bi metal jacket or steel core, which makes for a very poor anti-personnel round (very clean wound). The soviets were more creative with the x39, especially the FMJ's with the air bubble under the tip.
 
7.62x51 also called .308 (not x54)

So the air gap in the 7.62x39, makes it more effective than FMJ 7.62x51?
 
7.62x39 generally has a 125ish grain bullet (and most do not have special features such as air gaps under the nose). 7.62x51 is generally a 150ish grain bullet. 7.62x51 also has about 400fps over 7.62x39.

That means the NATO round flies in a flatter ballistic curve and will penetrate most materials better/deeper. Other than that, they will both drill a deep hole a little bit larger than 1/4". Except for a few special rounds here and there, both will be through and out a human body before they start tumbling.
 
I'm not sure about how both would react in a body, but the 7.62x39 runs around 2300fps and 1600ft.lbs. energy, while the .308 is up around 2800-3000fps and 2500ft.lbs energy. I'd say the .308 would probably be a lot more devastating to any bone or organs that got in it's way.
I wouldn't want to be shot with either.

Here's a place to compare ballistics: http://www.gunsandammomag.com/ballistics/?url=%2Fballistics%2F308_winchester.html&x=12&y=6
 
my762buzz,

Biggest difference is in effective range and performance at long range. The 7.62x39 is essentially a 300 yard/meter round. Sure the bullets will go further, but that is it's effective range. The 7.62x51 in M80 format is double that, and in M118LR configuration in a SWS, triple that.

Don
 
while the .308 is up around 2800-3000fps and 2500ft.lbs energy.
Click to expand...
In military loadings (ie. 7.62x51 FMJ as the OP asked), it's closer to 2700-2800fps. In commercial or reloaded .308, there's a million different loads and bullet weights. Much, much more than 7.62x39 has available.
 
Harder thump from the x51 round at pretty much all ranges (unless a super short x51 barrel is used -- down in the 11-13" range with 7.62x51 it looks a lot like 7.62x39 from a standard AK barrel ballistically, if I am not mistaken). The x51 round starts with quite a bit more energy, and the heavier bullets usually employed in x51 mean more retained energy down range. On the debit side, you get more recoil from x51 and it generally requires a heavier receiver and heavier weapon, so the x39 round is likely going to be fired from a quicker handling weapon, be it an AK, vz.58, SKS or whatever.

Most 7.62x39 FMJ ammo is notable for poor wounding potential, considering what it is and such. The standard Soviet M43 load was slow to yaw and unlikely to fragment, making most of the wounds it produced less impressive than the might have been. The Yugoslavs and possibly other people worked on this issue to make a Hague-legal but more damaging bullet design.

7.62x51, by comparison, has never been noted for poor lethality, though it's not the silver bullet that some people make it out to be (usually in comparison to rounds like 7.62x39 or, especially, 5.56mm).
 
I could see the extra weight and speed as more effective if the bullet expands, but if it does not expand does the heavier/faster bullet really
create more damage to a bone, internal organ tissue, etc?
Comparing 125 grains/2300 fps and 147 grains/2800 fps, does that extra 22 grains of weight and 500 fps cause a 30 caliber FMJ to become more lethal if both instances just pass through in a straight line?
Does the heavier/faster FMJ splinter bone better? Does it create a more intensive disruption of internal organ tissues?
 
Yes. A heavier bullet going faster will do more damage. The temporary cavity in particular will be larger (ballisticians correct me if I'm wrong...).
 
The higher velocity imparts a larger hydraulic force on the 308 causing it to tumble after less penetration, some of the west german 308 performed similar to m855 in 5.56, it had a similar steel core in the front and deep cannelure with thin jacketing casung it to fragment, the downside in weight and capacity giving rise to the 5.56 pattern rifles, and taking note of the wounds caused by a small diameter high velocity round, Russia designed the "poison bullet" the 5.45X39


M80.jpg


AK-47%20762x39mm.jpg


http://www.firearmstactical.com/wound.htm

and data from our very own JE223
http://www.brassfetcher.com/
 
You would be hard pressed to buy any M43(it's steel core) or fmj without an air gap in the tip or other feature designed to enhance wounding. Using Wolf or Golden Tiger 122gr fmj? Guess what, it's got a big air gap in the tip. Using Uly 124's? That's 8m2 effect, also an enhanced tumbler. Surplus Yugo? It's M67. So on and so forth. It's actually pretty ironic. We'd probably all be shooting M43 steelcore with its comparatively minor wounding effect if the banners hadn't gone after those nasty "cop killer armor piercing bullets." We can thank them for more effective small arms ammunition.
 
Interesting comparison between the 7.62x39 and 7.62x51. :) I think the main nice thing about 7.62x51, if you had to pick one characteristic, is it's better AP capability. Plenty of range, too. But either of them have .223/5.56x45 beat. :)

The only thing about .308/7.62x51 is the ammo cost, which hopefully will be coming down now that the terrorists in Iraq have been crushed in many areas since the surge of U.S. troops from a year and a half ago (less firefights = less ammo used = less demand for resupply = lower prices for us). It's always a good idea to have an SKS or an AK(M)-47, good punch, super reliable, and ammo costs quite a bit less. If cost is an issue, I'd get an AK. If potential resupply scenarios become an issue, it's going to be very helpful to have a 7.62x51 main battle rifle, though. It's nice to have one of each. :)

How many of you guys have an SKS or AK-47 of some variety?
 
The 308 will have about 400 FPS velocity advantage. The main advantage of higher velocity is greater effective range. The 308 will shoot a little flatter trajectory and be easier to hit with at longer ranges. The advantage of the 39mm round is that it fits in a more compact rifle.

With FMJ bullets this velocity advantage might translate into a slightly greater wounding and penetration advantage but on human targets I suspect any difference would be hard to detect. I think even a trained pathologist would be unable to tell the difference in wounds made by the two calibers.
 
The terminal characteristics depend more on the bullet's shape and construction and less on the cartridge. There are FMJ bullets for both the 7.62x39 and 7.62x51 that produce very different terminal results.
 
Twice as much energy, far longer effective range, and superior long range ballistics, for the .308.
Click to expand...

The original poster asked about "terminal performance", not "external ballistics".
 
I would say 7.62x51 is superiour only because the human body is not made only of soft, squishy tissue but also bones. The extra energy of the NATO cartridge may be enough to break through a bone that might otherwise deflect a shot from the Russian cartridge.
 
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