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Old May 12, 2014, 05:32 PM   #1
Duzell
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questions on building a 300 blackout upper (AR15)

now ive just finished my 5.56 upper and i was thinking of using another upper for 300 blackout (as i dont think i can get 308 in a ar15 only a ar10)

anyway

i was planning on using a 16" barrel fluted, but i was also told i can use some standard parts for a 300 blackout build

help and suggestions would be great , thanks
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Old May 12, 2014, 09:05 PM   #2
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well as no one could answer, this i found the answer myself. just needs a 300 blackout barrel
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Old May 13, 2014, 12:27 AM   #3
armed_librarian
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Just a barrel? yes. But I would recommend just building a dedicated upper. Wouldn't cost too much more. You can use the same BCG (as far as I know) and save a little there. Plus, if your running iron sights and not a dedicated optic, you would be re-siting every time you swap barrels.
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Old May 13, 2014, 07:22 AM   #4
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I'm not sure what you mean by "use some standard parts".
The only difference between 300AAC and .223 is the barrel/flash hider. Everything else is the same-gas system, BCG, upper receiver.
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Old May 13, 2014, 04:44 PM   #5
Duzell
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I was unsure and since these answer came after seem rather unhelpful. I'm already going to make a dedicated upper , but I'll reuse my handguard/bcg/charging handle as those are high end parts that I can't readily get
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Old May 13, 2014, 06:43 PM   #6
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Go check out 300blktalk.com

All the info you need on that cartridge and rifles for it
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Old May 14, 2014, 09:12 AM   #7
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I can see disaster in the making when parts are shared between 300 and .223 rifles. Suck up the cost and build a dedicated rifle or at least complete upper (including BCG) and conspicuously mark the unit with the caliber. Mark selected magazines also and separate them from your .22 stuff. As suggested above, go to the 300 Blackout forum for good assistance.
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Old May 14, 2014, 09:14 AM   #8
Unlicensed Dremel
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What twist rate should you choose for these if wanting to be able to shoot the longest/heaviest possible subsonic bullets?
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Old May 14, 2014, 09:30 AM   #9
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Quote:
Originally Posted by Unlicensed Dremel
What twist rate should you choose for these if wanting to be able to shoot the longest/heaviest possible subsonic bullets?
1:7 is the best twist rate for long subsonic bullets. But a lot of .300 BO barrels only come in 1:8, and that should be fine also.
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Old May 14, 2014, 04:32 PM   #10
Duzell
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well i already stated im doing a dedicated upper. its more of when i can afford them ill get this to be its own rifle. but as a project to see which i like better im going to try out the 300 on my 5.56 ar15 by swapping the barrel. and i dont think my bcg has issue. i already chatted with its designer paul leitner and he stated it can handle both no prob. its the black nitride bolt. it breaks in well so far. also already have dedicated magazine ive marked for the 300aac
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