Help interpret first chrony data

Discussion in 'Reloading' started by GSoD, May 28, 2008.

  1. GSoD

    GSoD Well-Known Member

    Messages:
    45
    Joined:
    Nov 22, 2007
    Hey all,

    So I bought a chronograph and ran my latest reloads through it. Can you help me interpret the data?

    I fired three loads of Varget at 44.4g, 44.5g, and 44.6g (each with federal brass, cci primers & 175g Sierra MatchKing in .308). I'm reloading with off the shelf Lyman and RCBS equipment and lee dies. I didn't seperate brass or bullets by volume or weight.

    Its being shot out of a Rem700P, off a bench with rests at both ends on a virtually windless day.

    I haven't played with getting closer to the lands because I want it to magazine feed so I've kept it at the book length.

    I posted the velocities, group sizes, standard deviation etc.

    I'm wanting to use this as my long range target round.

    I'm thinking 44.6 grains is in a good spot.

    Do you figure the velocities and deviations acceptable? If not, where should I start looking to improve?

    Any help appreciated.

    Thanks,

    ST


    ***44.4 GRAINS***
    GROUP1 shot at 100 yards
    Shot 1 2702 fps
    Shot 2 2718 fps
    Shot 3 2728 fps
    Shot 4 2726 fps
    Shot 5 2764 fps
    Avg Vel Grp1 2727.6 fps
    5 Shot Group Size 1.2 inches
    5 Shot Group MOA 1.256 MOA
    GROUP2 shot at 100 yards
    Shot 6 2710 fps
    Shot 7 2784 fps
    Shot 8 2812 fps
    Shot 9 2799 fps
    Shot 10 2821 fps
    Avg Vel Grp2 2785.2 fps
    5 Shot Group Size 0.547 inches
    5 Shot Group MOA 0.573 MOA

    Avg Vel Total 2756.4 fps
    Velocity Spread 119 fps
    10 Sht AVG Grp Sz 0.8735 inches
    10 Shot AVG MOA 0.915 MOA
    Bias Standard Dev 42.68 fps
    ***44.5 GRAINs***

    GROUP1 shot at 100 yards
    Shot 1 2821 fps
    Shot 2 2821 fps
    Shot 3 2821 fps
    Shot 4 2801 fps
    Shot 5 2775 fps
    Avg Vel Grp1 2807.8 fps
    5 Shot Group Size 0.56 inches
    5 Shot Group MOA 0.586 MOA
    GROUP2 shot at 100 yards
    Shot 6 2754 fps
    Shot 7 2702 fps
    Shot 8 2669 fps
    Shot 9 2655 fps
    Shot 10 2629 fps
    Avg Vel Grp2 2681.8 fps
    5 Shot Group Size 0.992 inches
    5 Shot Group MOA 1.039 MOA

    Avg Vel Total 2744.8 fps
    Velocity Spread 192 fps
    10 Sht AVG Grp Sz 0.776 inches
    10 Shot AVG MOA 0.812 MOA
    Bias Standard Dev 71.15 fps
    ****44.6 GRAINS****
    GROUP1 shot at 100 yards
    Shot 1 2603 fps
    Shot 2 2652 fps
    Shot 3 2680 fps
    Shot 4 2741 fps
    Shot 5 2731 fps
    Avg Vel Grp1 2681.4 fps
    5 Shot Group Size 0.553 inches
    5 Shot Group MOA 0.579 MOA
    GROUP2 shot at 100 yards
    Shot 6 2773 fps
    Shot 7 2746 fps
    Shot 8 2709 fps
    Shot 9 2723 fps
    Shot 10 2743 fps
    Avg Vel Grp2 2738.8 fps
    5 Shot Group Size 0.762
    5 Shot Group MOA 0.798

    Avg Vel Total 2710.1 fps
    Velocity Spread 170 fps
    10 Sht AVG Grp Sz 0.6575 inches
    10 Shot AVG MOA 0.688 MOA
    Bias Standard Dev 48.62 fps
     
  2. Forester

    Forester Well-Known Member

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    Mar 23, 2008
    The velocity spread seems high to me, can you tell more about how the brass was prepped? The groups seem good considering the high spread though.

    I have better luck with the 168gr bullets in my Savage .308. But others like the 175s so thats something else to try.
     

  3. KQguy

    KQguy Well-Known Member

    Messages:
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    Dec 7, 2007
    I like to see SD #'s in the single digits,I would try loads starting from the lowest to highest in .5 gr incraments.Once you find the best load,then you can start playing around with loads in .1 or .2gr incraments to find the "sweet spot".Be safe,and have fun.
     
  4. GSoD

    GSoD Well-Known Member

    Messages:
    45
    Joined:
    Nov 22, 2007
    KQguy - I did do the .3 increment workup initially to get into this ballpark as I got the best hits at 44.4 and 44.7.

    Forester - The brass is once fired federal that was factory loaded. I tumble cleaned, cleaned primer pocket, uniformed and deburred flashhole, trimmed to manual suggestion, deburred in and out, full length resize, measure neck run out and case neck thickness.

    I'm wondering if sorting by volume would help prevent such variation?
     
  5. KQguy

    KQguy Well-Known Member

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    Dec 7, 2007
    I would try a slower burning powder,and see how that works.
     
  6. GSoD

    GSoD Well-Known Member

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    Nov 22, 2007
    What would you suggest? It's going through a 26" barrel with 1/12 twist.

    I thought for sure Varget would work though as it seems very popular.

    But am open to suggestions.
     
  7. Forester

    Forester Well-Known Member

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    Mar 23, 2008
    Sounds good on the brass prep...did you sort by runout or neck thickness or just check that it is not excessive? You said cleaned primer pockets...did you uniform them as well as the flash hole?

    I know some like to FL size every time, but I have better luck neck sizing with a Lee Collet die. My brass does not get tight to chamber until about 4 or 5 firings...then I bump the shoulder and start again.

    How was your runout after seating the bullets?

    Edited to add: I have had good results from .308 Federal brass, but it seems soft and does not last as long. Lapua is way more consistent...and expensive. RE-15 is a slower powder, and gives me very good results.
     
    Last edited: May 29, 2008
  8. badaboom

    badaboom Well-Known Member

    Messages:
    330
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    Apr 30, 2007
    Not bad groups, seem pretty good.
    I prefer IMR4064 - 42.5 - 43.5 gr load - 175 BTHP match sierra. .308 caliber
    I also use Federal Gold Metal Match brass and Winchester large rifle primer.

    SD I prefer less than 50 FPS 100 MAX but as always the closer the better.
    I understand the magazine and chambering regarding your bullet length.

    I still adjust this to find the sweet spot then see if you can cycle the rounds
    you will most probably still be OK.

    Hope that Helps best of luck keep up the good work.
     
  9. GSoD

    GSoD Well-Known Member

    Messages:
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    Nov 22, 2007
    Thought I would provide an update:
    Looking at the numbers and the insight provided by this board and others I changed some things:
    a) gave my rifle a really good copper cleaning which it hadn't had in a few rounds.
    b) choronographed earlier in the day with more light and total overcast.
    c) got a digital scale. I've never been really comfortable with my working of the balance beam so I got a Lyman 1000 grain scale.
    I loaded up the same batches I ran through the last time and got much better numbers in terms of standard deviation and extreme spread (assuming I'm doing my math right). Here's the best one:
    44.5 GRAINS

    1) 2689 fps
    2) 2692 fps
    3) 2686 fps
    4) 2681 fps
    5) 2690 fps
    6) 2692 fps
    7) 2682 fps
    8) 2694 fps
    9) 2701 fps
    10) 2691 fps
    Avg Vel 2689.8 fps
    Extreme Spread 20 fps
    Deviation 5.55 fps
    10 Shot group size 0.717 inches
    10 Shot group MOA 0.685 MOA

    The group size got pushed out just a little bit by two hits that landed on the outside edge of the grouping, otherwise it would have been .5 inches. But at the time I had called them as flubbed shots so its something for me to work on.
    Thanks for all the help guys.
     
  10. .280Rem

    .280Rem Well-Known Member

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    Mar 25, 2008
    What is the purpose of this gun/round combo? From the looks of it, it suggest this is a paper puncher/target combo? I guess if you're going to punch paper inside 300yds, your velocity, or SD's wont make that much difference. Accuracy will rule. Im not a BR shooter, but understand they don't really care about SD as long as the accuracy is there. SD will become important at longer ranges though, but we're talking long range, and how precise do you want to be at those ranges. If you're SDs are in the 20fps range, unless you're trying to create one hole at 1000yds, I doubt it will make much difference. Probably none at all on plates out to 600yds. Others may have different ideas.

    Bottom line is I'm not sure what you really want interpreted?

    I do have one question from looking at a couple of the 5 shot strings...are you letting your bbl cool down sufficiently?

    Do you weight each charge individually?

    And, though I'm not a .308 loader, this "rule" holds true mostly across the board, or at least is my rule of thumb...use a powder that is fast burning enough to generate max velocity, but slow enough that the max velocity is attained at 90% or greater case fill. I think with the loads you listed, you're right at that with Varget. R-15 might be another choice. IMR 4064, BL-C(2) Also.