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Thread: Educate me on 10.5" and cans....

  1. #41
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    I dont necessarily believe that. But I wanted to remove that from the discussion. Since i was accused of being a "gemtech fan".

  2. #42
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    The first baffle will take the brunt of the unburned powder and be etched and well as the heat and flame will errode it - sooner than the subsequent baffles.

    Hence why some sell their suppressors with a "sacrificial baffle" mount -- Surefire's Muzzle is an example of this - the small ID at the muzzle end restricts the flame cutting and powder errosion that would be hitting the firt baffle.

    With this type of mount you really don't want to use it (tactically at least) w/o the suppressor.


    IIRC GemTech can no longer rebuild suppressors for the public, but I may be wrong.
    Kevin S. Boland
    Manager, Federal Sales
    FN America, LLC
    Office: 703.288.3500 x181 | Mobile: 407-451-4544 | Fax: 703.288.4505
    www.fnhusa.com

  3. #43
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    Essentially, if you're running a 10.5" bbl in 1/9 twist with a can on it, it's best to stick with 55 gr. bullets. Longer boat tail bullets, which also happen to be heavier, tend to yaw as they exit the muzzle. Hence the propensity to have baffle or end cap strikes. I have various cans in both QD & thread mount; one of which is an M4-02. If you have one, don't sweat it & just enjoy!

  4. #44
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    Cool

    I have a POF 9" upper, 1 in 7" twist with an AAC M4-2000 07. I have shot Hornady 5.56 75gr TAP ammo through it with no problems. I also have shot 62gr and 55gr ammo with no problems. The Hornady 556 TAP was very accurate too.

  5. #45
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    Quote Originally Posted by dancetiger View Post
    I have a POF 9" upper, 1 in 7" twist with an AAC M4-2000 07. I have shot Hornady 5.56 75gr TAP ammo through it with no problems. I also have shot 62gr and 55gr ammo with no problems. The Hornady 556 TAP was very accurate too.
    Yeah. There's a myth out there that the longer bullets have to be fired from a barrel longer than 10.5 to be stable. In other words, they need to be going fast.

    I've never subscribed to this rubbish.

  6. #46
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    I am the author of an iPhone app called BulletTwist. It computes a formula devised by Mr. Miller that is more advanced than Greenhill. This feature is also in my other app, BulletFlight -- a ballistic computer I did for KAC.

    The Hornady 75 grain AMAX is 1.070 inches long. A Sierra 77 is .985. A Barnes TSX 70 is 1.030.

    Here is a scenario:

    Hornady 75, 2400fps, 1:9 twist, 0 degrees F, 30.42 InHG air pressure - stability factor is just 0.90. NOGO.
    Change temp to 90 degrees F, and 29.92 pressure, and stability is 1.1. That is marginal, but it would look normal to a shooter.
    A shooter would post on an interweb forum "Works fine, you can shoot it." They would be giving bad advice because it won't work for someone after the temp drops.

    I like to check stability at 0 degrees F and a higher than normal atmospheric pressure to determine worst-case.

    Now back to 0 degrees F, 1:8 twist is 1.16 stability. Marginal. Not good enough.

    1:7 twist, stability goes to 1.51. Excellent.

    If you shoot AMAX 75 grain bullets at around 2400fps, you want a 1:7 twist, period. TAP 75 NATO ammo is
    perhaps the single best load for defense so that is why I want 1:7.

    If you shoot the Sierra 77, then 1:8 is fine If you shoot Sierra 69, you can do 1:9.

    At 2850 fps the Amax 75 is now ok in 1:8 but still not 1:9 unless it is warm out (around 70+).

    If you will ever do subsonic, then I would have to recalculate with about 800fps.

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