Help - developing 7mm stw load - questions

Discussion in 'Reloading Equipment and Components' started by jman41, Nov 24, 2011.

  1. jman41

    jman41 Member

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    Feb 20, 2011
    HELP! Been trying to develop a new long distance capable loads for my 7mm STW.
    Have chronographed a number of test loads and cannot get my feet on the ground.

    Rifle: Shilen DGA-M, new 26in, 1 in9" stainless barrel under a S&B PMII 5x25 DT cm scope. Have shot in new barrel with over 75 shots w/ correct cleaning process. Gun shoots consistent 1/2"MOA @ 100yds. Having problem getting FPS up over 3000 fps. Load specs: Federal 215 Lr. Mag Primers, Fireformed (once fired) Rem Cases, Retumbo Powder and Ber ger 168 gr. VLD bullet set off lands @ 0.030"

    Test bullet used: 168 gr Berger VLD Hunting

    Have chrono'd 5 shot groups as follows:
    7MM STW BERGER 168 GR VLD ----AVG FPS COUNT
    String 1 78.1 GR Retumbo ----------2924.8 ----5
    String 2 78.3 GR Retumbo ----------2814.7 ----5
    String 3 78.5 GR Retumbo ----------2817.6 ----5
    String 4 78.8 GR Retumbo ----------2868.3 ----5
    String 5 79.0 GR Retumbo ----------2942.5 ----5
    String 6 79.8 GR Retumbo ----------2919.8 ----5
    String 7 80.5 GR Retumbo ----------2896.5 ----5
    String 8 81.0 GR Retumbo ----------2904.5 ----2

    My objective is to push load up over 3000 fps. Note String 1 load has high 2924.8 avg. fps, String 5 load is highest but still can't get bullet past 3000 fps.

    Shot in barrel using several boxes of commercial HSM Gold Trophy (same) 168 gr. Berger VLDs, chrono'd HSMs loads at 3195 avg. fps (20 rounds).

    Pushed powder load to big time max in String 8, but more Retumbo doesn't seem to push 168 gr. Berger any faster using 2 grains of addtional powder?

    CAN ANYONE GIVE ME SOME ADVICE ON WHY?
    Have prepared new test loads using other powders, RL22, IMR 7828 and 4831SC. Just need to get down to the range to test and chrono.

    ADVICE WELCOME!
     
    Last edited: Nov 24, 2011

  2. badaboom

    badaboom Well-Known Member

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  3. jman41

    jman41 Member

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    Sorry new to forum, thanks for your advice
     
  4. mtang45

    mtang45 Well-Known Member

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    Apr 9, 2005
    jman,

    Your barrel may be to short for Retumbo and the extra powder is just going up in a fireball. I shoot a 7mm STW with 30" Shilen 1/9 barrel and have no problem hitting 3100 fps using Retumbo, so try a slightly faster powder like H1000.

    Let us know how that works and welcome to the forum!
     
  5. jman41

    jman41 Member

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    Feb 20, 2011
    Thanks mtang45
    Already loaded up new stepped 3 shot strings using H1000, 7828 and RL-22.
    I'll report back with results!

    Again, thanks!