Atomic Ammunition Subsonic mixed with some 10.4 and A Surefire can
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Thread: Atomic Ammunition Subsonic mixed with some 10.4 and A Surefire can

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    Default Atomic Ammunition Subsonic mixed with some 10.4 and A Surefire can

    Range Report with Atomic Ammunition Cycling Subsonic 556. I was interested in some subsonic 556 for my 416 UBL raid gun clone after having a new born and loving to shoot at all hours of the day. Run down on the gun is a Remarked MR556. 10.4 barrel chop. Franklin BFS trigger, Surefire SB2.. Everything else pretty much standard the factory HK parts. First magazine was unsuccessful at ejecting the empty cartridge. Took a step back into the garage and swapped out the HK buffer/spring for a standard GI buffer and spring, I assume H2 buffer. Ran awesome. Very quite and fun to shoot. The only issue ive seen is key holing. I never expected a 10inch gun with subs to be accurate but did find it interesting with the bullet tumbling. My target was set up about 50 yards away and at a standing position, and fairly quick rate of fire. I swapped back the HK buffer and spring along with some Federal XM855s and accuracy picked up a great deal along with the noise. 0 baffle strikes but im very curious as to why it key holes...but Im more curious about running the GI Spring and Buffer for any longevity or parts failure. My understanding this over gasses the weapon. All in all its a great concept especially to keep noise down or low recoil for children to have fun at the range.
    Attached Thumbnails Attached Thumbnails Atomic Ammunition Subsonic mixed with some 10.4 and A Surefire can-20191019_081723_1571495902195.jpg   Atomic Ammunition Subsonic mixed with some 10.4 and A Surefire can-20191019_084101_1571496024779.jpg   Atomic Ammunition Subsonic mixed with some 10.4 and A Surefire can-20191019_084231_1571496119203.jpg  
    Last edited by JDMYERS88; 10-19-2019 at 04:06 PM.
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    The bullet tumbles because 1/7 twist won't stabilize the heavy bullets the subsonic rounds use. That's one of the reasons subsonic 5.56 isn't really practical for anything.

    The buffer and spring won't 'over gas' anything. It's overgassed with all the factory parts in it when you shoot NATO spec ammo, but they do that for reliability in adverse conditions.

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    Quote Originally Posted by eodinert View Post
    The bullet tumbles because 1/7 twist won't stabilize the heavy bullets the subsonic rounds use. That's one of the reasons subsonic 5.56 isn't really practical for anything.

    The buffer and spring won't 'over gas' anything. It's overgassed with all the factory parts in it when you shoot NATO spec ammo, but they do that for reliability in adverse conditions.
    Im going to try some 77 grain and see if I get some improvements. The rifle is definitely fun to shoot but like you mentioned its not practical for much.

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    I have never has any success getting that Atomic ammo to cycle reliably through any of my suppressed short barreled AR's?

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    Subsonic 5.56 is just not very practical and not reliable. If you want to suppress rifle rounds subsonic, 300 Blackout is the way to go. Much better ballistics then 5.56 also.

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    The twist rate has nothing to do with the keyholing. It's the barrel.

    MR556 barrels simply don't like under powered ammunition and I suspect is has something to do with the tapered bore.

    I've had consistent keyholing with wolf ammunition of every bullet weight whereas all NATO spec or heavy commercial grade (such as Hornady 75 grain TAP) ammunition runs fine.

    Keep in mind that the 1/7 rifling twist was initially designed for heavier/longer M855 and M856 tracer. The heavier the bullet, the tighter the twist to stabilize correctly.

    Hell, even Atomics own literature says to use 1/7 or tighter twist.
    Last edited by InshallahTech; 10-24-2019 at 07:55 AM.

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    Thanks for the report--- keep a "special" magazine (with subsonic ammunition) for intruders!!!

    Tony

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    Quote Originally Posted by InshallahTech View Post
    The twist rate has nothing to do with the keyholing. It's the barrel.

    MR556 barrels simply don't like under powered ammunition and I suspect is has something to do with the tapered bore.

    I've had consistent keyholing with wolf ammunition of every bullet weight whereas all NATO spec or heavy commercial grade (such as Hornady 75 grain TAP) ammunition runs fine.

    Keep in mind that the 1/7 rifling twist was initially designed for heavier/longer M855 and M856 tracer. The heavier the bullet, the tighter the twist to stabilize correctly.

    Hell, even Atomics own literature says to use 1/7 or tighter twist.

    I agree 1/7 should be enough to stabilize. There has to be something else at play like he mentioned that is causing the keyholes.
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    I too haven't had any success in reliable subsonic 5.56 in suppressed SBRs. At least out to distance without tumbling.

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