Results 1 to 8 of 8

Thread: Accuracy vs Standard deviation

  1. #1
    Join Date
    Dec 2019
    Posts
    3

    Accuracy vs Standard deviation

    Just curious, for your 600 yd match load what is your accuracy and standard deviation? For now I am using 42.5 grains of varget w/ a Sierra 168 mk with an asd is 14 but it prints a .668 inch 5 shot group at 200 yds. My twist is a 12 on a factory 26" 700. With rl15 I've had a lower sd but the group was larger. Just want to know what some of you have settled with and feel comfortable competing with. Thanks

  2. #2
    Join Date
    Jan 2004
    Location
    Tualatin, Oregon
    Posts
    296
    Bottom line for any load is "how goes it group?" In another shooting sport (long range highpower), there was s discussion about using AA-2520 for 1000 yard loads for an international competition. It produced low ES and SDs - and would not group. Since Varget was not available in the US (1992), the powder selected was IMR-4895. As an aside, many shooters from overseas stated that the ammo was some of the most accurate they ever fired.

    Hope this helps.

  3. #3
    Join Date
    Dec 2006
    Location
    Branchville, NJ
    Posts
    499
    For many years, the go to load for 600 yard Hi-Power was 168gr SMK and 41.5gr IMR-4895. This was the standard back in the 80's when I started shooting.

  4. #4
    Join Date
    Aug 2016
    Posts
    27
    In the card game of 600-1000yd F-class competition precision trumps ES/SD every hand. For poops and giggles I recorded velocities for complete 60 shot plus sighter 600yd F-open matches on two occasions with a Labradar. One match was 599 and the other 598 for score. The ES of that load was in the upper 40's fps and the SD was in the upper teens. I have many 20 shot cleans on that load at 600yds and one 1000yd clean with 12x (6.5 x55 BJAI/ Precision Ballistics 142/ 2920-40 fps range). I've had loads that tested at under 5fps spread for 8 shots that grouped 1.5-2.0" at 300yds in testing and loads that had 18fps spread that shot in the .8"'s repeatedly at 300yds. I shoot the load that has the best groups and also has very acceptable groups a couple of tenths of charge weight above and below it. Since I am tuning for a specific distance (600 and 1000yds....and a load that shoots .3 MOA at 600 usually does near the same at 1000) this same load shoots about .5-.6" in an 8 shot group at 100yds. When I tuned at 100yds for groups in the .2's it always opened up at distances 300yds and beyond.

  5. #5
    Join Date
    Dec 2019
    Posts
    3
    Thanks to all of you guys for the responses. Rardoin thanks that's what I needed to hear. Sometimes it's hard to know what to do or look for without the practical experience. I'm getting started in ftr in the near future but I've been struggling with the sd thimg for a while based off what a program says what the bullet spread can be at a given range with a high sd. Thanks guys

  6. #6
    Join Date
    Dec 2019
    Posts
    3
    An after thought, why tune loads for a specific range?

  7. #7
    Join Date
    Dec 2003
    Location
    washington.........STATE that is.
    Posts
    10,708
    Quote Originally Posted by mcevermj View Post
    An after thought, why tune loads for a specific range?
    Because a load can ONLY be tuned to one specific place. 100 shots of varying velocities can only pass thru one point in space.

    Think about throwing a pass in football, it takes a different velocity to lob to the receiver VS firing it flat yet both converge at the receiver

    (as long as you're >insert fahv'rite footballer here< )

  8. #8
    Join Date
    Aug 2016
    Posts
    27
    Quote Originally Posted by mcevermj View Post
    An after thought, why tune loads for a specific range?
    Since you are posting in the F-class section I'll use it as an example. Although a rifle/load can be tuned to be 'pretty darned good' at 100-1000yds if you get the mix just right (so to speak) it will have a distance that it will definitely group best. If you are shooting LR BR and need .3 MOA and under to win then you won't likely be happy at 1000yds with the 'one hole' .0xx" 100yd group load so you'd best tune at least at 600yds (preferably 1000yds) to be competitive. In F-class I am looking for a load that will group .3MOA or under at 300yds in different conditions/different days with at least a 5 shot group. IME, if my rifle is doing that consistently then I can get it to shoot cleans at 600 to 1000yds with a high X-count. However, when I tune at 100yds the variables in my testing are not as visible between test groups as at 300yds and I can get fooled at times. I will say that the loads that shoot in the 0.1xx" at 100yds (5-8 shots, F-open rifle) have NEVER been my best loads at 600 and beyond and usually open up in MOA disproportionately to what it shot at 100yds. All that being said, for F-class rifles I find if I can get .3MOA precision at 300yds it carries to .5MOA and under vertical at 600 and 1000. One issue with testing at 600 and beyond is the high variation in environmental variables that are not easily seen and accounted for that can affect results. I find 300yds being a good compromise for longer being closer to the competition distance yet also being able to have better 'controls' on conditions.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •