120g SIERRA HPBT MATCH KING +AA2520

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  • MISSEDBYMILES

    120g SIERRA HPBT MATCH KING +AA2520


  • #2
    Here you go!

    A COAL of 2.260" is the norm for 5.56 NATO, not so in the Grendel. With the array of projectiles in the 6.5mm, COAL is going to vary widely. For instance, when loading for the 100g Amax; if you seat it longer than 2.200" you begin to lose neck tension and the recommended per/caliber of support for the projectile. Make sure you have a COAL measurement (for the chamber in your rifle) for each type of projectile you plan to load for, or you my experience artificial over-pressure.

    Last edited by Guest; 08-15-2012, 06:56 AM.

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    • rasp65
      Warrior
      • Mar 2011
      • 660

      #3
      The 120 SMK is shown in the AA data as having a max charge of 30.6 gr of AA2520 powder. It has proven to be a good load. By my measurements the Sierra 120 SMK is .036" shorter than the 123 gr Hornady "head". I measured a COAL of 2.37" with the SMK. What do you use for tails, AA recommends CCI450.

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      • Dogue
        Warrior
        • Mar 2011
        • 415

        #4
        The 120 SMK does have a more rounded ogive than some of the others, 123 Scenar or Amax for example. In my gun I'm touching the lands at 2.25" with 120 SMKs but don't touch till 2.284 with 123 Amax's.
        Μολὼν λαβέ

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        • #5
          Originally posted by Bwild97 View Post
          ...A COAL of 2.260" is the norm for 5.56 NATO, not so in the Grendel. With the array of projectiles in the 6.5mm, COAL is going to vary widely. For instance, when loading for the 100g Amax; if you seat it longer than 2.200" you begin to lose neck tension and the recommended per/caliber of support for the projectile. Make sure you have a COAL measurement (for the chamber in your rifle) for each type of projectile you plan to load for, or you my experience artificial over-pressure...
          Nicely said!

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          • MISSEDBYMILES

            #6
            Thanks for the quick replys guys .
            I never thought of the difference in neck tension with the 120g Sierra compared to 123g LAPUA SCENARS what I had been used for years ,
            Just gose to show you it is ALWAYS BETTER TO ASK SOMBODY BEFORE YOU DO SOMETHING STUPID .
            Thanks again .

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