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View Full Version : Terminal ballistics 7.62x39 vs 5.45x39 for 8-10" barrel?


cmace22
05-24-2011, 8:11 AM
I was wondering if anyone could help me out with this. I havent been able to find any info of which of these two rounds perform better (terminal ballistics) wise.

Say we are comparing both rounds form an 8" Krink barrel.

I understand that the 5.45 will have a higher velocity but would the mass of the 7.62 give a better wounding profile.

If you had to choose between the two based solely off wounding characteristics which would you choose and why.

My personal thoughts would be the 7.62x39 given its mass and velocity would be the clear winner over the lighter but faster 5.45x39.

Im not concerned with debating the legalities of SBR's.

Whatcha think?

Thanks


Chad

Snapping Twig
05-24-2011, 11:35 AM
You say 8 to 10 inch barrel, then the 7.62x39 might be the better choice.

Here's why...

Both depend on barrel length to completely burn the powder charge to accelerate the bullet, but the 5.56/.223 depends on it more.

The powder used in each is different also. The 7.62x39 uses a slightly faster powder, so it theoretically needs less barrel to burn completely.

Bullet weight comes into play as well and the 7.62x39 uses a bullet that is from two to three times heavier than the 5.56/.223 and that translates into more mass which is useful.

The typical velocities for these rounds are 1000fps different with the 5.56/.223 being the faster of the two, but in a short barrel the speed differential is not so pronounced, this is where mass makes a difference in the 7.62x39 and it becomes "more equal".

The 5.56/.223 is a little pill hot rodded to make it something it would not otherwise be and it is successful. The 7.62x39 is more or less equivalent to the old 30-30 and has muscle on its own.

Enjoy your experiment and I hope you find the one that suits you best.

Quickdraw Mcgraw
05-24-2011, 11:42 AM
:useless:

pyro3k2
05-24-2011, 12:00 PM
I think what kind of ammo you use in both cartriages would be more important than which one. If we are talking FMJ vs FMJ then I would have to side with the 5.45x39 but if you planning on using HP, PSP, or bullets of that nature then I would have to side with the 7.62x39

cmace22
05-24-2011, 12:03 PM
Thank you for the info.

I think what kind of ammo you use in both cartriages would be more important than which one. If we are talking FMJ vs FMJ then I would have to side with the 5.45x39 but if you planning on using HP, PSP, or bullets of that nature then I would have to side with the 7.62x39

It would be crappy Wolf FMJ vs crappy Wolf FMJ.

Why would you side with 5.45x39?

pyro3k2
05-24-2011, 12:35 PM
Thank you for the info.



It would be crappy Wolf FMJ vs crappy Wolf FMJ.

Why would you side with 5.45x39?

In FMJ the 5.45x39 would leave a more significant wound profile then a FMJ 7.62x39. The 47 round would just punch a hole through the target and not transfer much, the lighter 74 round will tumble, yaw, and fragment. The 47 round usually starts to fragment, yaw, and tumble around 8 inches of penetration to where reports have the 74 ammo as early as 2.5 inches and as late as 4 inches of penetration. Again this is FMJ vs FMJ, when you start using HP, SP, or hunting bullets you can have the 47 round do the same as the 74 round, if FMJ is it then 5.45x39 all the way.

pyro3k2
05-24-2011, 12:46 PM
Just a fun little video
4q_JURu8CTY

zfields
05-24-2011, 12:51 PM
pretty sure the newer wolf military classic uses the more modern 7.69 FMJ round, which has a similar depth of penetration before it tumbles, and similar construction as the 5.45 ( hollow cavity to encourage the tumbling effect)


You cant compare old 7.62 FMJ to 5.45 as far as wound profiles.




For the record, I keep Soft point rounds in my AK, I would rather use SP in either caliber then depend on a tumbling bullet : )

Stone
05-24-2011, 1:12 PM
Say we are comparing both rounds form an 8" Krink barrel.

I understand that the 5.45 will have a higher velocity but would the mass of the 7.62 give a better wounding profile.

If you had to choose between the two based solely off wounding characteristics which would you choose and why.

Frangible ammunition is undoubtedly the most damaging, but only if it has enough velocity to fragment. Look up the fragmentation velocity for 5.45, then you should be able to consult from a table the maximum fragmentation range when fired from a barrel of any particular length. If you can stay within fragmentation range then it will surely do more damage than a 7.62

Beyond that range, you are better off with 7.62 because it will preserve its momentum better, thereby being less deflected by wind, and doing more damage through yawing or boring a larger diameter hole than a non-fragmenting "pellet" would.

If you are hunting big game and you don't want to damage the meat or the pelt then 7.62 is also better at close range.

cmace22
05-24-2011, 1:22 PM
In FMJ the 5.45x39 would leave a more significant wound profile then a FMJ 7.62x39. The 47 round would just punch a hole through the target and not transfer much, the lighter 74 round will tumble, yaw, and fragment. The 47 round usually starts to fragment, yaw, and tumble around 8 inches of penetration to where reports have the 74 ammo as early as 2.5 inches and as late as 4 inches of penetration. Again this is FMJ vs FMJ, when you start using HP, SP, or hunting bullets you can have the 47 round do the same as the 74 round, if FMJ is it then 5.45x39 all the way.


Interesting. Would the drop in velocity from an 8" barrel adversely effect the 545 round more so than 7.62x39 or vise versa.


Frangible ammunition is undoubtedly the most damaging, but only if it has enough velocity to fragment. Look up the fragmentation velocity for 5.45, then you should be able to consult from a table the maximum fragmentation range when fired from a barrel of any particular length. If you can stay within fragmentation range then it will surely do more damage than a 7.62

Beyond that range, you are better off with 7.62 because it will preserve its momentum better, thereby being less deflected by wind, and doing more damage through yawing or boring a larger diameter hole than a non-fragmenting "pellet" would.

If you are hunting big game and you don't want to damage the meat or the pelt then 7.62 is also better at close range.

Thats the million dollar question then. If the primary wounding characteristics of the 545 come from fragmentation like in the 556, what is the minimum velocity at which that occurs. If its the yaw thats the primary characteristics then at what minimum velocity can yawing occur?

pyro3k2
05-24-2011, 1:32 PM
Interesting. Would the drop in velocity from an 8" barrel adversely effect the 545 round more so than 7.62x39 or vise versa.




Thats the million dollar question then. If the primary wounding characteristics of the 545 come from fragmentation like in the 556, what is the minimum velocity at which that occurs. If its the yaw thats the primary characteristics then at what minimum velocity can yawing occur?

I've read that the 5.45 isn't dependant on velocity to fragment and that it preforms the same out of a Krinkov as it would a traditional 16 inch ak74. But I have a very hard time buying that. My 5.45x39 has a 16 inch barrel so I can't give any first hand experience on a shorter barrelled 74 :(

cmace22
05-24-2011, 1:32 PM
It looks like you would loose about 500 fps with an 8" barrel bringing the MV down to about 2500 fps for 545 and about 2000 fps for 762x39


It looks like 5.45x39 is a really good round.

Stone
05-24-2011, 3:24 PM
Thats the million dollar question then. If the primary wounding characteristics of the 545 come from fragmentation like in the 556, what is the minimum velocity at which that occurs. If its the yaw thats the primary characteristics then at what minimum velocity can yawing occur?

Well I know the 5.56x45mm generally needs at least 2500 fps to reliably fragment, though it depends on the bullet weight. As for the 5.45, I do not know much, but it seems that I may have spoken too soon by regarding it as frangible; I'm reading more reports of it being prone to yawing and not fragmenting at all.

http://pictures.second-amendment.org/albums/userpics/10001/223-ballistics-1.jpg
http://i710.photobucket.com/albums/ww103/aplorton/mil_rifle_wounds.jpg

nrakid88
05-24-2011, 3:34 PM
I would go 7.62x39 for the short barrel. I think a 16'' barrel gets 2300 fps, and a 7'' PWS diablo, now the 107 i believe, upper was getting 2000fps, so 7.62x39 is great for short barrels. I am planning on a draco sbr, and a 11.5'' 7.62x39mm ar upper in the future.