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All things 300 AAC BLACKOUT
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 Post subject: 300BLK vs 7.63x39
PostPosted: Fri Jan 27, 2012 3:32 pm 
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On AAC's website, they claim that the 125g loading in 300BLK "matches ballistics of the 7.62x39".
The 123g 762x39 can hit 2600fps per wikipedias info.The 300 with a 125g (only 2g difference) only goes 2215 fps. Seems to me the 7.62x39 much better down range ballistics than the 300. Can anyone explain AACs comment?


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 Post subject: Re: 300BLK vs 7.63x39
PostPosted: Fri Jan 27, 2012 4:08 pm 
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Prkshooter wrote:
On AAC's website, they claim that the 125g loading in 300BLK "matches ballistics of the 7.62x39".
The 123g 762x39 can hit 2600fps per wikipedias info.The 300 with a 125g (only 2g difference) only goes 2215 fps. Seems to me the 7.62x39 much better down range ballistics than the 300. Can anyone explain AACs comment?


The optimized 300 BLK bullets have a better BC.... see http://www.300blktalk.com/forum/viewtopic.php?f=128&t=78824 for example

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 Post subject: Re: 300BLK vs 7.63x39
PostPosted: Fri Jan 27, 2012 4:12 pm 
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Sure. Apples to apples is what you are missing.

Real world -

USA Brand ammunition is the ideal choice for training-or extended sessions at the range or in the field. As you'd expect, USA Brand Centerfire Rifle Ammunition features high quality and reliability at an economical price. Symbol: Q3174 Caliber: 7.62x39mm Bullet Weight: 123 Grains Bullet Type: Full Metal Jacket Test Barrel Length: 20" Velocity in Feet Per Second: - Muzzle: 2355

^^ That is Winchester ammo, measuring the velocity from a 20" bbl.

300 BLK, 125 gr OTM 2230 ft/s, 1380 ft-lb

^^

Remington ammo. I think it is important to remember you have to compare one major manufacturer to another. If we compare Double Tap to Winchester, Double Tap will win every time - on paper.

From AAC's .pdf, that is 300 out of a 16" bbl

If you measured the 300 out of a 20" bbl, I'd imagine you will get the same or slightly higher velocity.

The 7.62x35 projectiles tend to have a superior BC and fly with less velocity loss as compared to range.


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 Post subject: Re: 300BLK vs 7.63x39
PostPosted: Fri Jan 27, 2012 4:43 pm 
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curious sam wrote:
Sure. Apples to apples is what you are missing.

Real world -

USA Brand ammunition is the ideal choice for training-or extended sessions at the range or in the field. As you'd expect, USA Brand Centerfire Rifle Ammunition features high quality and reliability at an economical price. Symbol: Q3174 Caliber: 7.62x39mm Bullet Weight: 123 Grains Bullet Type: Full Metal Jacket Test Barrel Length: 20" Velocity in Feet Per Second: - Muzzle: 2355

^^ That is Winchester ammo, measuring the velocity from a 20" bbl.

300 BLK, 125 gr OTM 2230 ft/s, 1380 ft-lb

^^

Remington ammo. I think it is important to remember you have to compare one major manufacturer to another. If we compare Double Tap to Winchester, Double Tap will win every time - on paper.

From AAC's .pdf, that is 300 out of a 16" bbl

If you measured the 300 out of a 20" bbl, I'd imagine you will get the same or slightly higher velocity.

The 7.62x35 projectiles tend to have a superior BC and fly with less velocity loss as compared to range.



That is true, Robert specifically set the SAMMI test barrel length for 300 BLK to 16". much shorter than typical

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 Post subject: Re: 300BLK vs 7.63x39
PostPosted: Fri Jan 27, 2012 7:47 pm 
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For that I used the example of the $40 Lapua ammo. 300 BLK also does well compared to another good 7.62x39mm load - the Hornady V-MAX.

The problem is you (and everyone) incorrectly assume 7.62x39mm velocities are reported from 16 inch barrels.

Remington UMC BC 0.290 PSI, 2295 fps 16" - $12.00 a box at Midway.
Brass cased.

Hornady V-MAX BC 0.260 PSI, 2350 fps 20" - $13.80 per 20.
Steel cased.

Hornady velocity from a 16" barrel, according to QuickLoad, 2241 fps (based on 2350 from a 20 inch barrel).

At 50 yards, the 7.62x39mm has 4 ft-bs more energy.
At 100 yards, the low-cost UMC 300 BLK has 14 ft-lbs more energy.

At 300 yards, the low-cost UMC 300 BLK has 8.8% more energy.
At 300 yards, the 125 Match 300 BLK has 23.1% more energy.


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 Post subject: Re: 300BLK vs 7.63x39
PostPosted: Fri Jan 27, 2012 10:11 pm 
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That clears up alot! Thank you for your input. Makes me even more exited about getting my model1 sales upper.


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 Post subject: Re: 300BLK vs 7.63x39
PostPosted: Fri Jan 27, 2012 11:52 pm 
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300Blk wrote:
The problem is you (and everyone) incorrectly assume 7.62x39mm velocities are reported from 16 inch barrels.


Hey now, not everyone 8)


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