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300 Blackout Questions Again...

This is a discussion on 300 Blackout Questions Again... within the Ammunition forums, part of the M14 M1A Forum category; Originally Posted by Dave P Ram, QL does include a 300-221 (300 Whisper). Is that not what you want? The case/cartridge dimensions and the max ...


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Old November 17th, 2012, 11:50 AM   #16
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Originally Posted by Dave P View Post
Ram, QL does include a 300-221 (300 Whisper).

Is that not what you want?
The case/cartridge dimensions and the max pressure information is slightly different between the two so I created my own case using the SAAMI specs. When you compare the two, the Blackout has slightly more case volume and the max pressure is 5,000 psi greater.

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Old November 17th, 2012, 12:17 PM   #17
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I had some interest the 300 black and variations until I found out what it's ballistics were. If I remember correctly, once you get into the 150 grain plus bullets, the trajectory starts looking like a parabola. I forgot what joelogic's load was when he won the Bay Area Rifle Championship this year in his class. It was something like a 15" drop at 200 yds...might have been 168's.

Myself, I went 7.62 x 39 route...economics and a colt uppper to go on my preban colt lower...

Rammac...what bullet weight would you suggest for the 300 black if you wanted to duplicate or slightly exceed 7.62 x 39 w/ 124 grainers ballistic wise.

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Old November 17th, 2012, 02:48 PM   #18
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Originally Posted by Mocos View Post
I had some interest the 300 black and variations until I found out what it's ballistics were. If I remember correctly, once you get into the 150 grain plus bullets, the trajectory starts looking like a parabola. I forgot what joelogic's load was when he won the Bay Area Rifle Championship this year in his class. It was something like a 15" drop at 200 yds...might have been 168's.

Myself, I went 7.62 x 39 route...economics and a colt uppper to go on my preban colt lower...

Rammac...what bullet weight would you suggest for the 300 black if you wanted to duplicate or slightly exceed 7.62 x 39 w/ 124 grainers ballistic wise.
Do you mean internal ballistics or trajectory?

As far as internal ballistics, I don't think you can get very close due to the case volume differences, the Blackout has a lot less volume. I think that pressure and velocity-wise the best you can do in the Blackout is about 200 fps slower than the 7.62x39 cartridge. You might push a 125gr bullet to about 2200 fps (the Hornady manual recommends no higher than 2100 fps) but that would be at the very top end of the rifle's capability and you would be pushing the chamber pressure pretty high. This all based on a 16" barreled AR.

As for trajectory, I played with the data a little but it looks like you can get the 110gr bullets to perform pretty close to the way the 124gr does in the 7.62x39. The Hornady manual lists a H110 load using the 110gr bullets that results in about 2400 fps. That's in the range of the muzzle velocity for the 124gr 7.62x39 and the energy is only about 300 foot-pound feet (ft-lbf) less at the muzzle. At 500 yards there is only about a 5"- 6" drop difference and the energy difference is about 100 ft-lbf. Both loads hold drops of no more than about 2" out to 150 yards and then they start to drop pretty quickly.

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Old November 17th, 2012, 05:57 PM   #19
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Rammac,

As usual, thank you for your excellent advice and information. I did not get the manual yet, but maybe tomorrow.

Sapp

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Old November 17th, 2012, 06:29 PM   #20
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Consider it a new daddy present, even if I missed the other occasions.

Thanks from SAPPNASTY
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Old November 18th, 2012, 07:34 AM   #21
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Quote:
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Do you mean internal ballistics or trajectory?

As far as internal ballistics, I don't think you can get very close due to the case volume differences, the Blackout has a lot less volume. I think that pressure and velocity-wise the best you can do in the Blackout is about 200 fps slower than the 7.62x39 cartridge. You might push a 125gr bullet to about 2200 fps (the Hornady manual recommends no higher than 2100 fps) but that would be at the very top end of the rifle's capability and you would be pushing the chamber pressure pretty high. This all based on a 16" barreled AR.

As for trajectory, I played with the data a little but it looks like you can get the 110gr bullets to perform pretty close to the way the 124gr does in the 7.62x39. The Hornady manual lists a H110 load using the 110gr bullets that results in about 2400 fps. That's in the range of the muzzle velocity for the 124gr 7.62x39 and the energy is only about 300 foot-pound feet (ft-lbf) less at the muzzle. At 500 yards there is only about a 5"- 6" drop difference and the energy difference is about 100 ft-lbf. Both loads hold drops of no more than about 2" out to 150 yards and then they start to drop pretty quickly.
Thanx, that's pretty much what I thought. I think the most compelling thing about the 300 black is the facility to convert to that caliber utillizing existing AR components. For me, it was the economics and the availbility of the ammunition. Sorta like the razor is cheap....its the cost of the blades that get you. The recent forum Travis Haley cllip on the 300 black out to 750 yds certainly got a lot of interest. I don't recall him saying what load data he was using or what adjustments in elevation was required. I suspect that in time, the 300 black ammo will come down in price but no where near AK round surplus.

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Old November 18th, 2012, 10:52 AM   #22
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I agree, I think the real appeal is to somebody who has an AR platform and wants different caliber options. For a guy like me I just don't see the advantage unless I buy a couple of uppers at the same time. I like the cartridge a lot for CQB work and if I were in to 3-gun competitions I'd probably look at getting one, the lack of recoil with a .30 cal impact looks really appealing.

I will say that it seems to me that if the barrel were longer, maybe a 20", you might be able to make up some velocity and energy using the 120 - 125 grain bullet weights and get closer to the AK performance.

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Old November 18th, 2012, 01:35 PM   #23
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Quote:
Originally Posted by RAMMAC View Post
I agree, I think the real appeal is to somebody who has an AR platform and wants different caliber options. For a guy like me I just don't see the advantage unless I buy a couple of uppers at the same time. I like the cartridge a lot for CQB work and if I were in to 3-gun competitions I'd probably look at getting one, the lack of recoil with a .30 cal impact looks really appealing.

I will say that it seems to me that if the barrel were longer, maybe a 20", you might be able to make up some velocity and energy using the 120 - 125 grain bullet weights and get closer to the AK performance.

Or someone who want to hunt with there Ar and can't becuase of caliber restrictions.

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Old November 18th, 2012, 01:39 PM   #24
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Mocos,
You say you went with 7.62 X 39 with your Colt AR lower, does that mean that you load the AK rds in AR mags? I based my choice of 300BLK on the commonality of parts to the .223 guns (only the barrel is different) and the fact that I had read of reliability issues with the AK rd in AR type guns. I had looked at those AR lowers that accepted AK mags but that route meant that I'd have a completely different AR type gun with different bolt, barrel and lower. I have not done ballistic calculations using any of the programs, but by using load data that I got online, I worked up a load using a 147 gr bullet that gets way more than 2200 fps out of my 18" barrel without showing pressure signs in the primers. I'd be interested to see how it compares as far as drop and accuracy to the 7.62 X 39, but I don't own a suitable gun to compare the two side by side.

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Old November 18th, 2012, 02:15 PM   #25
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Or someone who want to hunt with there Ar and can't becuase of caliber restrictions.
Good point, it isn't much different than hunting with a .30-30 but with the advantage of the AR gas gun design.

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Old November 18th, 2012, 02:19 PM   #26
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Mocos,
You say you went with 7.62 X 39 with your Colt AR lower, does that mean that you load the AK rds in AR mags? I based my choice of 300BLK on the commonality of parts to the .223 guns (only the barrel is different) and the fact that I had read of reliability issues with the AK rd in AR type guns. I had looked at those AR lowers that accepted AK mags but that route meant that I'd have a completely different AR type gun with different bolt, barrel and lower. I have not done ballistic calculations using any of the programs, but by using load data that I got online, I worked up a load using a 147 gr bullet that gets way more than 2200 fps out of my 18" barrel without showing pressure signs in the primers. I'd be interested to see how it compares as far as drop and accuracy to the 7.62 X 39, but I don't own a suitable gun to compare the two side by side.
Post the load specs and I can run the info through my QuickLoad and QuickTarget software for the internal ballistics (pressures and such) and trajectory info.

I would need case volume or just the brand of case.
The bullet brand and weight.
The powder and charge weight.
Overall cartridge length.
Barrel length (obviously you already posted that).

I'm curious about the info too and would be happy to make a comparison against whatever rifle and load you prefer.

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Old November 18th, 2012, 04:00 PM   #27
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I may have confused the results that I got with the 147's and the 125's
I will search further for the 147gr load data but
this is the load info I have located so far.
for my loads with 125gr SMK and 125gr Speer TNT bullets loaded into new Remington 300BLK brass with 21.5 gr of LIL Gun powder at a col of 2.275" I got between 2,509 and 2,557 fps out of my 18" 1/10 300BLK barrel, this is a compressed load. When loading 155 Lapua sceiners in the same brass with 16.5 gr of LIL GUN to a col of 2.235" I got a best of 2,073 fps.

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