Shot Groups

Discussion in 'Long Range Hunting & Shooting' started by liltank, Aug 21, 2009.

  1. liltank

    liltank Well-Known Member

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    So when determining the OA group size for a long range hunting capability... what measurement do you consider for your load development? Example: I shot a group that measured 1.041 out side to out side, but if you subtract .308 for bullet size that leaves a group of .733 center to center. Also, I have been getting a lot of groups with two cutting the same whole and flier of 1/2 to 5/8 of an inch from the two touching. Should I consider these loads as good because it is possibly me, or do I dump the load and try something else? For development I generally shoot 3 shot groups unless I find something I really like and then move to a 5 shot group. Trying to conserve on powder and bullets.

    Just as a back up to my abilities, I have cut 5 shot groups in the .25 MOA range and can consistently hold .75 MOA or less. Can a loose primer pocket in a load batch of brass with tight primer pockets be my fliers? What I mean by loose, is they go in real easy, but don't fall out even when tapped on something hard.

    Well hope this is enough info for an assessment of my situation.

    Thanks in advance,
    Tank
     
  2. J E Custom

    J E Custom Well-Known Member

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    I consider 100yard groups just a starting point and a measure of SDs and velocities.

    Group size will normally increase as distance increases. Example : A 1" group at 100 yards
    will almost all ways be 10"+ at 1000 yards and shooter ability is magnified at longer distance.

    For Long range hunting the size of the game and distance to be hunted has a lot to do with
    the needed group size.

    Most set there max group size @ 1/2 MOA at any distance under perfect conditions and shooting
    skills.

    Obviously you want it to be better if possible and custom rifles are capable of 1/4 MOA if tuned
    and loaded correctly.

    I have to rely on a great shooting rifle for long shots because it gives me confidence and I try
    not to shame myself because I know that if I do my part it will do it's.

    One good group does not make a long rang rifle But a consistent one does.

    So the best group you can shoot consistently is what you have to live with and will limit the
    distance you should shoot.

    I normally use 300 yards as a good judge of whether I can use it for long range load
    development .If it does well then I increase the distance to it's limits and decide if
    this is the load to use for the type of hunting I will be using the rifle for.

    I hope this will help.

    J E CUSTOM
     

  3. liltank

    liltank Well-Known Member

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    Thanks JE, but what about my flier and the other questions stated?

    Tank
     
  4. J E Custom

    J E Custom Well-Known Member

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    Primer pockets should be snug so the don't leak @ firing. They will seal but any movement can effect your load quality.

    I would do the test this way. First fire a round and push a patch through the barrel (Dry)
    Then repeat the process in a short time so the barrel begins to warm up. Have a target on
    the bench with you and plot each shot as you fire them and number them.

    After 4 or 5 rounds you should see which ones are the fliers. The use of a chrony is
    recommended for the test.

    With the target and the chronograph this is what you should find = If the first few shots
    group well and the 3,4 or 5Th shot is a flier Then it is probably the stock to barreled action
    fit. Bedding, action screw torque, tip pressure ,ETC.

    If the fliers are random the chronograph will help determine if it is a load problem with the
    load combination.

    And in my case sometimes I just have a bad day but this process tells me when even if I
    don't recognize it at first.

    I hope this helps because it can be frustrating.

    J E CUSTOM
     
  5. winmagman

    winmagman Well-Known Member

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    liltank,

    Play with your seating depth, some times .005 or .010 longer or shorter can bring those fliers back to the rest of the group.

    Chris
     
  6. liltank

    liltank Well-Known Member

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    Yeah, that is my next line of thought. I have started to play with the depth a little. That is where I have found some accuracy. I am going to have to lengthen them out again to see if the lands are the preferred setting again. Thanks for the input.

    Tank
     
  7. liltank

    liltank Well-Known Member

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    Well I think I fixed the problem. I dropped a full grain and lengthened my COL (Thanks winmagman for the reminder). What I did find, is that my Savage doesn't like a clean bore. The dirtier it got the faster it shot and the grouping stayed tight. The first shot was my comparator shot. The second after cleaning the barrel went about .25" high and .75" to the right. I decided to keep it dirty for the 3rd and 4th shot. They stacked up in the first shot and my speed increased by 50fps. Does this make sense?

    Tank
     
  8. J E Custom

    J E Custom Well-Known Member

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    Some barrels like a fouled/seasoned barrel ,if yours is one of them you may have to shoot
    15 or 20 rounds and then do a light cleaning (Not back to bare metal).

    Work out your cleaning regiment and then your first cold bore shot will be the one that
    counts.

    Most of my rifles like a fouling shot and a dry patch then I am ready to go hunting.

    J E CUSTOM
     
  9. HUAINAMACHERO

    HUAINAMACHERO Well-Known Member

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    Liltank,
    Good to know you got your problem solved.
    I am picking up the tips also for my groups.
    Thanks for the teaching:)
    My 270 win barrel also likes a dirtier barrel.
     
  10. winmagman

    winmagman Well-Known Member

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    I've got a couple that do the same thing. First couple of shots after cleaning register slower on the Chrony and don't shoot to the same POI as the following shots. Once the barrel fouls some, pressures build a little higher, and things settle down to where they belong.

    Chris
     
  11. liltank

    liltank Well-Known Member

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    Thanks guys for the input. It help calm the nerves!!!:rolleyes: Kids didn't help any though. The range time helped clear my head.:D

    Tank
     
  12. elkaholic

    elkaholic Well-Known Member

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    I noticed a couple of things that haven't been mentioned. Besides the fouling raising pressures, there are at least two other things that will make quite a difference in firing a string, especially in in light barrel. As the barrel heats up, the bore constricts slightly which increases pressure. Even more dramatic, which you can prove with your crono is heating the powder inside your case after it is chambered. The longer you aim, the more the pressure increases in a warm (hot) barrel. Some studies show as much or more as 1 1/2 fps for every degree in temp increase. Hope this helps. God bless.......Rich
     
  13. silvertip-co

    silvertip-co Well-Known Member

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    Measuring a group to three decimal points is all a bunch of gun magazine hokus pokus. I dont care if they do make an outside micrometer to do it more accurately. You're measuring holes cut in a product that is highly changable due to thickness, dierction of grain, % moisture, temperature , etc. A 1/2" group is no more accurate than a .50" group or a .500 group. It's just like fluted barrels and the Browning barrel tuning thing hung on the end of the rifle... all hokus pokus.
     
  14. liltank

    liltank Well-Known Member

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    So how does this answer my questions? Thanks for your opinion though.

    Respectfully,
    Tank