Need a 300 blackout subsonic load with widener 175

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  • Jul 3, 2010
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    Re: Need a 300 blackout subsonic load with widener 175

    I have an 8" noveske and 12 grains of H4198 will cycle the bolt at about 950fps but unburnt powder in coming back down the gas tube. I guess I need a faster burning powder, maybe?
     

    country888

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    Jan 2, 2011
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    Re: Need a 300 blackout subsonic load with widener 175

    Use AA1680 between 11gn and 11.7gn depending on your barrel length. I use 11.3gn and works fine around 1000fps
     

    SpeedyR

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    Re: Need a 300 blackout subsonic load with widener 175

    might want to check the hand load forum on the 300 blackout forum...

    http://www.300BLKTALK.com/forum/viewforum.php?f=141

    but in general from the research i've done as I look to build a 300 upper, 1680 seem s to be the "go to" powder for reliable function in ARs for subs.

    if you are running a bolt gun you might have more options.
     

    CPRifle

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    Re: Need a 300 blackout subsonic load with widener 175

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: country888</div><div class="ubbcode-body">Use AA1680 between 11gn and 11.7gn depending on your barrel length. I use 11.3gn and works fine around 1000fps </div></div>

    What length barrel are you running? Mine is an 8" Noveske. Some AA1680 should be arriving at my door today. I would've guessed almost a full grain lower based on the limited data I've seen (and based on 10.8gr being common for 220s).

    I'll reply with after I get out to the range to test and chrono.
     

    CPRifle

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    Re: Need a 300 blackout subsonic load with widener 175

    Well country888, looks like you were spot on. I just tried 10.2 to 10.8gr of AA1680 with 175 SMKs and velocities were 833-929fps. Based on these velocities I predict that 11.3 should get me around 1000fps.
     

    CPRifle

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    Re: Need a 300 blackout subsonic load with widener 175

    I've concluded that 10.2gr (AA1680) with 225gr Hornadys and 11.3gr with 175 SMKs both yield close to 1000fps.

    I find it interesting that the lighter bullet requires more powder to achieve the same velocity. Also, the 11.3gr load (175 SMK) has a noticeably louder action noise.