Velocity question

Discussion in 'Ammunition & Reloading' started by ktmboyz, Jun 12, 2012.

  1. ktmboyz

    ktmboyz New Member

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    I have loaded up a trial batch today of 55gr BT-fmj Hornady bullets with LC cases, cci sm primers and 21.7 gr or IMR 3031 @ 2.200 C.O.L.


    All the books and reference I can find are saying these should be pushing 27-3000 fps depending on what reference you use.

    I ran some through my Chrony today and the fastest I had was 2417 and slow or around 2350. I was using an older 16" AR upper I have that I know is pretty worn but functions ok. All the rounds cycled ok and seemed to have plenty of pressure. Why am I getting such difference from spec to chrony ??

    The cases all look good also .
     
    Last edited: Jun 12, 2012
  2. TLuker

    TLuker Active Member

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    What rifle were the books using? I've noticed that most books seem to use something with a high rate of twist and a long barrel to get their data. Shorter barrels then come in at lower velocities. I think they intentionally use longer barrels just for a safety factor?
     

  3. Chandler51

    Chandler51 New Member

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    Aren't the velocity numbers usually generated with a 20-22 inch bbl?
     
  4. ktmboyz

    ktmboyz New Member

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    Ya I know barrel lenghts affect it but I didn't think 4-500 fps
     
  5. JonM

    JonM Moderator

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    if i remember right its like 100-200fps per inch depending on powder burn rates. so that sounds right for test data from a 20" barrel
     
  6. JTJ

    JTJ Well-Known Member Supporter

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    Personally I dont use 3031. My Lee book shows a starting load of 22.3 grains with a max of 25.0 and 3165 fps for the IMR 3031. The owner of one of the gun shops is a competitive target shooter and he put me on to Varget. I use Varget or H335. I dont have a chronograph so I cant tell you what the speed is out of my 16" barrel.
    http://www.ballisticsbytheinch.com/223rifle.html
     
  7. ktmboyz

    ktmboyz New Member

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    I had some I wanted to use up, thats why I was using it and I have read good results with it. I think I am going to stick with AR comp.
     
  8. steve4102

    steve4102 New Member

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