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PostPosted: Sat Dec 26, 2009 8:43 pm 
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The 7.62x39 has been espoused as being a great caliber from 0-300m, but is it really?

So, many of us know that the 7.62x39 isn't exactly a flat-shooting caliber (unless a rainbow is considered, 'flat'). But, how much of a rainbow is it really?

I took some ballistics data and decided to make a chart just to show the drop of the round at distance.

This is for a 123gr FMJ with a muzzle velocity of 2300fps. Standard 50/100m zero (they have the same POA/POI, which should be clue #1).

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As you can see, at 200m, you get a drop of 7 inches. Not too terribly bad but when you go beyond 200m, the drop is better described in feet rather than inches (seriously).

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Conclusion: If you've been lying to yourself that your AK is, 'just as good' at 400m as an AR-15, just stop. Stop right now. There is a very good reason why the Russians have now been using the 5.45 longer than the 7.62x39.

This is not a thread bashing the Kalashnikov rifle and should not be taken as such. This is a thread about knowing the limitations of your platform and more specifically, your caliber.

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PostPosted: Sat Dec 26, 2009 8:52 pm 
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Wow, great info! Thanks for the heads up. That is quite the drop past 200.

How does the 5.45x39 compare?

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PostPosted: Sat Dec 26, 2009 8:55 pm 
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In some respects it's worse than that Dave, how many rifles in 7.62x39 have a 2 inch offset? Isn't it a bit less than that? A smaller sight/bore offset will only make things worse. Given that most military style combat is at 75 yards and less it may not be that big a deal but given that it impacts the rounds versatility I understand the point you are pushing here.


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PostPosted: Sat Dec 26, 2009 8:55 pm 
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yup, and this is why (among other reasons) I moved to 5.56/.223 (i know they are not the same either) from my SKS. You get what you pay for :) I shoot my SKS just fine inside of 100 yards with iron sights but wanted something that could reach out a little past it's capabilities.


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PostPosted: Sat Dec 26, 2009 8:56 pm 
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BHP wrote:
In some respects it's worse than that Dave, how many rifles in 7.62x39 have a 2 inch offset? Isn't it a bit less than that? A smaller sight/bore offset will only make things worse. Given that most military style combat is at 75 yards and less it may not be that big a deal but given that it impacts the rounds versatility I understand the point you are pushing here.


The iron sights on an AK are 1.875" off of the bore.

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PostPosted: Sat Dec 26, 2009 8:59 pm 
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Yep, a second look at your graph shows you have it just under 2 inches and not at 2 inches. Didn't notice that before.


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PostPosted: Sat Dec 26, 2009 9:02 pm 
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That graph also demonstrates clearly why the rifle/round should be zeroed at 100.
Im not saying you cant shoot beyond that but that would be the optimum distance.
You can still hold on target at about 150 (at that range a 2 inch difference is forgivable).
It will keep you shooting at 0 from 50-100.


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PostPosted: Sat Dec 26, 2009 9:04 pm 
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DavePAL84 wrote:
This is not a thread bashing the Kalashnikov rifle...

Just the cartridge it's chambered for... :wink:

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PostPosted: Sat Dec 26, 2009 9:05 pm 
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SCIENCE!!! IT WORKS, BITCHES!!!

Thanks Dave, that's some real eye-opening data.

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PostPosted: Sat Dec 26, 2009 9:16 pm 
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crypto wrote:
SCIENCE!!! IT WORKS, BITCHES!!!

Thanks Dave, that's some real eye-opening data.


Absolutely - you have any windage info? Wind for .223 @300 isn't much of a deal but I'd think the stubby x39 bullets would get blown off the map.

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PostPosted: Sat Dec 26, 2009 9:21 pm 
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hmm im curius then how the "tabuk ak" compares since it seems to be more a dmrish type gun.http://en.wikipedia.org/wiki/Tabuk_(firearm)


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PostPosted: Sat Dec 26, 2009 9:25 pm 
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It's not a sniper rifle? But I put a scope and a Dragunov stock on it...

I never gave much thought to the trajectory of the 7.62.x39, but it makes sense. Given that the the bullet itself weighs 3 times as much as the 5.45 but there's a similar powder charge (or so I'd think).

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PostPosted: Sat Dec 26, 2009 9:32 pm 
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This is the second thread I've read today (the other by Nimbadwhatever) that mentions the arc of bullets. To be honest I never really gave much thought to it. I know they say that x round has a flatter trajectory they y round, but that never seemed to mean much to me.
This has been a real eye opener, the graphic being the real kicker. Thanks a lot Dave! You (and Nimba) have actually taught me something today. I learned today. Yay!

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PostPosted: Sat Dec 26, 2009 9:37 pm 
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Pardon my ignorance in the realm of bullet trajectory but...

If my 7.62x39 round has a drop of 2.9 feet at three hundred meters how am I able to consistenly hit a torso target at that distance while aiming high center with a rifle zeroed at 50 meters? Shouldn't I land every round way low/off target?


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PostPosted: Sat Dec 26, 2009 9:40 pm 
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Rick12337 wrote:
hmm im curius then how the "tabuk ak" compares since it seems to be more a dmrish type gun.http://en.wikipedia.org/wiki/Tabuk_(firearm)


The Tabuk gets a little better velocity (and thus a slightly flatter arc due to its 24" barrel vs a normal AK), but I dont really know how much of a difference it would make.

As far as shooting out of windows at targets across a plaza or square though, Im sure it would get the job done just fine, as the MOUT is still a short-range battleground.

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PostPosted: Sat Dec 26, 2009 9:46 pm 
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cmoney wrote:
Pardon my ignorance in the realm of bullet trajectory but...

If my 7.62x39 round has a drop of 2.9 feet at three hundred meters how am I able to consistenly hit a torso target at that distance while aiming high center with a rifle zeroed at 50 meters? Shouldn't I land every round way low/off target?



Could be the setting you zeroed at. If you set the tangent sight at 100m and zeroed, then moved the sight to the 300m or battle sight zero, it will realighn the rifle. I zero AKs to POI=POA at 100m with the tangent sight sent on 100m. I can ring the big steel gong (not a great feat, its big at my range) every time after reagjusting to 300m. Same with the 30'' gongs at 200m at my old range.

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PostPosted: Sat Dec 26, 2009 9:48 pm 
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phil_in_cs wrote:
crypto wrote:
SCIENCE!!! IT WORKS, BITCHES!!!

Thanks Dave, that's some real eye-opening data.


Absolutely - you have any windage info? Wind for .223 @300 isn't much of a deal but I'd think the stubby x39 bullets would get blown off the map.



The 7.62X39 bullet is approx 123 grains as opposed to the 5.56mm round that weighs approx 62 grains. So if I read this right how is a .223 better?? They are both meant to injure and make casualities in combat.


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PostPosted: Sat Dec 26, 2009 9:51 pm 
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aa1pr wrote:
They are both meant to injure and make casualities in combat.


Negative ghost writer. They were both designed to KILL in combat.

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PostPosted: Sat Dec 26, 2009 9:52 pm 
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Oh yeah I can see how it would have a trajectory like a rainbow, the Ruskies would have known this as well, IIRC it also has a rather low stability, it kind of cork screws a bit in flight.

Having said that you have to look at the tactics the USSR troops used, dropping individual targets at extended range was never the riflemans job, the soviets had drags and the machine guns for laying down fire in depth as the infantry advanced.

One fact, if you have hundreds of guys with AKs going at an objective with sights set at a longer range, say 400, the looped trajectory may drop rounds inside trenches and dug in positions as its coming in at steeper angle at longer ranges. The .303 for instance was known for it's looped trajectory at very long ranges, the Vickers gun was used by British forces as an indirect fire weapon, using the sustained fire kit you could literaly put fire over a hill straight down on to the heads of the enemy. You use the looped trajectory to make it rain bullets, at 500 rounds per minute on a tripod it works.


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PostPosted: Sat Dec 26, 2009 10:07 pm 
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olbaid_dratsab wrote:
cmoney wrote:
Pardon my ignorance in the realm of bullet trajectory but...

If my 7.62x39 round has a drop of 2.9 feet at three hundred meters how am I able to consistenly hit a torso target at that distance while aiming high center with a rifle zeroed at 50 meters? Shouldn't I land every round way low/off target?



Could be the setting you zeroed at. If you set the tangent sight at 100m and zeroed, then moved the sight to the 300m or battle sight zero, it will realighn the rifle. I zero AKs to POI=POA at 100m with the tangent sight sent on 100m. I can ring the big steel gong (not a great feat, its big at my range) every time after reagjusting to 300m. Same with the 30'' gongs at 200m at my old range.


I'm not using an AK in that anecdote, its an AIA 7.62x39 enfield, rear sight isn't adjustable, only front sight...


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PostPosted: Sat Dec 26, 2009 10:10 pm 
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Could the AIA be fitted with an Enfield ladder sight?


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PostPosted: Sat Dec 26, 2009 10:19 pm 
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I still don't think a 12.7 ft drop over 500 meters is really enough to make it be coming down with a rain effect. 12.7 ft at 500yds = about 30 MOA. 1 MOA is equal to 1/60 of a degree. so 30 of those would equal to half a degree. Thats not a very steep incline. It would make it impossible to shoot through a window if your target was 100 meters behind the window, but its not going to turn AKs into mortars.

I'm going to edit this a little for a fuck up on my part.

I forgot that the bullet will be desending from it's maximum ordinant or apex. It won't be desending from the shooter's location. So imagin the the apex being about 2/3 inbwteen the shooter and target. This means it will start its 12.7 ft desent at about 330 yd from teh shooter. This makes it drop 12 ft over aboout 166 yds there by making the angle a lot steeper. It still doesn't seem like the angle would be steep enough to make it like a mortar. Lemmy fuck around with a calculator a lil bit and see if i can get something.


Ok I just did some quik stuff. I rounded the 12.7 to just 12 and the 166yds to 200. I got a 72 MOA drop. thats about 1 3/15 degree angle. Still not enough to make it rain.

By all means check my shit. I was rounding a good bit and kind of doing it on the fly w/o much thought or with out writing shit down. So I could be wrong, I'm not good at math.

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Last edited by olbaid_dratsab on Sat Dec 26, 2009 10:36 pm, edited 1 time in total.

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PostPosted: Sat Dec 26, 2009 10:29 pm 
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12+ ft drop at 500m? :shock:

Thanks for the write up, never looked up this sort of info before, got my attention. Gonna look into it a bit more and see what else I see, don't own anything in that caliber (but will eventually) still good info to tuck away.

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PostPosted: Sat Dec 26, 2009 10:53 pm 
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What was the ambient temperature for the 2300 fps velocity, somewhere in the 70 - 80 degree F range? Those EXTREMELY cold Russian winters should give the 7.62x39 the trajectory of a well thrown rock!!!

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