300 blackout ballistics by the inch

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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Leu-cifer
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300 blackout ballistics by the inch

Post by Leu-cifer »

anyone have a good reliable source for ballistics of the most commonly commercially available and popular 300 blackout roundish relation to barrel length and rifling?

I was at first considering a 9" barrel with a 1:7 rifling, for that is what the cartridge was designed around. I will mostly be shooting supersonic loads at first, and will possibly later on mount a suppressor (strongly leaning towards the OSS suppressor).

and while we are on the barrel topic, what are some of the best companies to buy from for a high quality and high durability 300 blackout barrel and have a good quality control process? price isn't an issue for this build, it only will determine how much I'll have to save for it.
tallburnedmidget
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Re: 300 blackout ballistics by the inch

Post by tallburnedmidget »

Leu-cifer wrote:anyone have a good reliable source for ballistics of the most commonly commercially available and popular 300 blackout roundish relation to barrel length and rifling?

I was at first considering a 9" barrel with a 1:7 rifling, for that is what the cartridge was designed around. I will mostly be shooting supersonic loads at first, and will possibly later on mount a suppressor (strongly leaning towards the OSS suppressor).

and while we are on the barrel topic, what are some of the best companies to buy from for a high quality and high durability 300 blackout barrel and have a good quality control process? price isn't an issue for this build, it only will determine how much I'll have to save for it.

I don't think there is one source. Also I would suggest looking at bullet speed (FPS) for barrel lengths. If you can use Google to search over this site you can find a good amount of information about with posted load data where you can find speed of the load along with the barrel length.

Once you get a ballpark of max speeds guys are getting with bullets for certain barrel lengths you can use the JMBallistics Calculator here: http://www.jbmballistics.com/cgi-bin/jb ... mp-5.1.cgi.
Then you can pick all kinds of bullets and enter the Max FPS and distances to get a ton of ballistic information.

I am a hunter and from my own personal experience I did not like my 7" barrel for hunting. The max velocities were so low that I was going to be stuck hunting with ONLY the 110gr Blacktip and I found that off putting since the caliber is so flexible. I decided to move up to a 10.5" barrel and it was a good acceptable choice between 16" and a really short barrel.

I still prefer the 16" barrel for the most versatility of the caliber but I can still have a little benefit with a 10.5" barrel. I still am giving in and I am loading 110gr Blacktips for it but hell, that is no too big of a deal as it is a great hunting bullet :)
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stengun
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Re: 300 blackout ballistics by the inch

Post by stengun »

Howdy,

I would be interested in seeing someone take a 20" barrel and test the velocity by cutting off one inch at a time down to 6 or 7".

One of the groups that I follow on Facebook ( don't remember which one) has done this with various calibers from the .338 Lapua, .300WM, .308, 7.62x54R, to .223.

A similar test for the 300 BLK would be great.

Paul
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dellet
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Re: 300 blackout ballistics by the inch

Post by dellet »

stengun wrote:Howdy,

I would be interested in seeing someone take a 20" barrel and test the velocity by cutting off one inch at a time down to 6 or 7".

One of the groups that I follow on Facebook ( don't remember which one) has done this with various calibers from the .338 Lapua, .300WM, .308, 7.62x54R, to .223.

A similar test for the 300 BLK would be great.

Paul
I've got a 24" barrel, ammo and a chop saw, you got a couple hundred to donate to the cause?
300 Blackout, not just for sub-sonics.
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TreeTopFlier
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Re: 300 blackout ballistics by the inch

Post by TreeTopFlier »

stengun wrote:Howdy,

I would be interested in seeing someone take a 20" barrel and test the velocity by cutting off one inch at a time down to 6 or 7".

One of the groups that I follow on Facebook ( don't remember which one) has done this with various calibers from the .338 Lapua, .300WM, .308, 7.62x54R, to .223.

A similar test for the 300 BLK would be great.

Paul
Until someone chops one up... Heres and old chart but gives a good feel for it. http://www.silverdoctors.com/wp-content ... 208801.png

For what its worth, rounds that give me 2250 fps in a 16 inch run around 2050 fps in my 8.5"
I build the #TTFPowderStand for the Lee Turret Press

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TKO
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Re: 300 blackout ballistics by the inch

Post by TKO »

Rule of thumb has been 25 fps loss per inch.

This has proven to be very close with my 8" compared to velocities posted for 16". YMMV
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stengun
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Re: 300 blackout ballistics by the inch

Post by stengun »

TKO wrote:Rule of thumb has been 25 fps loss per inch.

This has proven to be very close with my 8" compared to velocities posted for 16". YMMV
That's true but if you will check some of the test results some times that's not the actual results.

On some of the no-magnum rounds barrel length over 24" didn't help much and in some cases even reduced velocity.

It would be neat if someone did chop down a barrel. Heck, I've seen 16" barrels listed for $89.00 so chopping one up for science wouldn't be be a huge out of pocket expense. You would spend more money on the ammunition.

Maybe I'll try this one day after I complete my other 1,237 projects that I'm working on.

Paul
I'm so Liberal that I work at the Bill & Hillary National Airport!!!
TexasEric
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Re: 300 blackout ballistics by the inch

Post by TexasEric »

dellet wrote:
stengun wrote:Howdy,

I would be interested in seeing someone take a 20" barrel and test the velocity by cutting off one inch at a time down to 6 or 7".

One of the groups that I follow on Facebook ( don't remember which one) has done this with various calibers from the .338 Lapua, .300WM, .308, 7.62x54R, to .223.

A similar test for the 300 BLK would be great.

Paul
I've got a 24" barrel, ammo and a chop saw, you got a couple hundred to donate to the cause?

Put up a link or message me. I will donate a bit to the cause. We can pick ammo used for the test.
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Dolomite_Supafly
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Re: 300 blackout ballistics by the inch

Post by Dolomite_Supafly »

Already been done. There is a spreadsheet showing velocities at barrel lengths up to 30".
WWW.thegunmilitia.com

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Tom12.7
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Re: 300 blackout ballistics by the inch

Post by Tom12.7 »

There are quite a few variables to work out there besides barrel length.
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