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Achieved my lowest SD ever

Discussion in 'Reloading' started by TexMex247, May 14, 2019.

  1. TexMex247

    TexMex247 Well-Known TGT Supporter

    May 11, 2009
    Leander(NW Austin)
    I guess if you don't own a chronograph this probably doesn't mean much to you but I recently attained the lowest SD I have ever had in any gun I load for... and I have reloaded a dozen different calibers over the last decade.

    Last year, I finally bought myself a 308. Specifically a Howa 1500 with 20" heavy barrel. Not being able to leave well enough alone, I started reloading for it as soon as I had about 60 once fired cases in hand.

    As it happens the rifle likes both PPU's Match line and Federal's 168gr/175gr SMK GMM factory offerings. Naturally I bought some 168 SMK bullets and scoured the net for info. I wound up working with RL 15 and worked up a few loads.

    All of them(42-44gr) were MOA loads if I did my part behind the trigger but a node around 42.5gr seemed to be the sweet spot for me. I started exploring this range when I put down a .501" 5 shot group at 103 yards last month.

    I decided to do a primer test just to see if I could reduce my spreads a little within that area. The winner was a load of 42.4gr of RL15 using a Fed210 primer and PPU once fired brass that achieved an average of 2449 fps an ES of 4 and an SD of 1 !

    Now technically I think the SD is 1.7 and the sample size was only 5 shots but either way, I'll take it. I have put together many accurate and consistent loads over the years but this one takes the cake. I didn't sort bullets, cases, turn necks, use match primers, just found that magic powder bullet combo.

    Overall that group was just over an inch but I haven't settled on a COL just yet and luckily the howas box magazine will allow bullet length near 2.890" which will put me well into the lands with just about any bullet out there.

    For any of you long rifle types I'm sure you'll appreciate the relevant data. It may not mean much at 100 yards but at 600 yards a few fps makes a difference. Happy reloading gents !

    Big Dipper and Vaquero like this.
  2. Vaquero

    Vaquero Pre-ban Staff Member Admin

    Apr 4, 2011
    Out West
    That's just negligible variance.
  3. robertc1024

    robertc1024 Test Test Test TGT Supporter

    Jan 22, 2013
    San Marcos
    That's mighty nice. I've never gotten below 4 or so. Bought some Lapua brass to try to help with that.
  4. ZX9RCAM

    ZX9RCAM Over the Rainbow bridge... TGT Supporter

    May 14, 2008
    The Woodlands, Tx.
    What is SD?
  5. Dawico

    Dawico TGT Addict

    Oct 15, 2009
    Lampasas, Texas
    Standard deviation. The velocity spread across the tested loads.

    Strangely enough all shots being within 1 or 2 fps of each other (which is very good) usually does not produce the tightest groups.
    ZX9RCAM and toddnjoyce like this.
  6. dee

    dee Well-Known

    Nov 22, 2008
    Red River Way
    Your numbers may not stay that tight with rl15. It's not overly temp stable so as temp swings it may raise or lower as velocity will.

    Sent from my SM-G965U using Tapatalk
  7. FireInTheWire

    FireInTheWire Hold me beer and watch this TGT Supporter

    Jan 22, 2018
    Big Country
    Congrats! very nice man
  8. orbitup

    orbitup Sticker Cop TGT Supporter

    Nov 6, 2010
    South of Dallas
    Nice. I got this the other day with my 308 and Peterson small primer brass.

  9. TexMex247

    TexMex247 Well-Known TGT Supporter

    May 11, 2009
    Leander(NW Austin)
    As it happened, the 4 of 5 shots were exactly 2450fps. One somewhere in the middle was 2446.

    It's true this wasn't my best group of the day but on a couple of previous range trips I put down a few .5-.6" 5 shot groups. I never did chrono those rounds but they looked damn good on paper.
  10. TexMex247

    TexMex247 Well-Known TGT Supporter

    May 11, 2009
    Leander(NW Austin)
    What's your barrel length and powder charge on those Orbitup?
    I feel like anything under an SD of 5 is something worth reproducing.

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