muzzle velocity veriation

Discussion in 'Reloading' started by snojnke, Nov 11, 2013.

  1. snojnke

    snojnke Active Member

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    What is an acceptable variation of muzzle velocity. I notice if I put into my ballistics program 70fps less its a whole MOA at 1000 yards. Not that I've seen that much but I have seen 40 fps difference in a shot string.
     
  2. g0rd0

    g0rd0 Well-Known Member

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    too many problems with that question.
    1, how accurate is your chrono?
    2, how accurate are you with your powder charges?
    3, how much vibrations are in your barrel?
    We can keep on with this for many many replys. so you need to ask yourself some questions If your reloads are giving you good accuracy and your chrono says that you have a huge extreme spread why worry.
    My favorite hunting load (according to my friends chrono), has es of 80+/- fps and I still have 5 shot groups under 1 inch @ 100 meters. My fav target load (using the same chono), has -25 fps es but, the accuracy remains the same (under 1 inch @100 meters).
    The only difference is target loads / less powder (different powder also), less speed std primer = less recoil and velosity but, the accuracy remains the same
    Hunting loads / more powder, mag primer, lots more vel and lots more recoil but same accuracy.
    So, I believe that the accuracy to es problem that I have is in my head and not with my rifle
     

  3. varmintH8R

    varmintH8R Well-Known Member

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    I completely agree with your assessment that actual performance is more important than chrony readings. BUT - I would not use 100m testing as any indication of that. To really understand if extreme spread is spoiling groups, you'll have to shoot at your max range.

    I'm attaching a picture of a target shot at 100yards shot doing a max charge test on a 22-250. It is 8 shots, with 8 different charge weights. Total extreme spread was 315fps. There is VERY little verticle dispersion at 100 yds. I have another target shot with 280AI and 168 Bergers that also shows less than 1" at 100 under a similar test (about 265ES). Bottom line - validate your drops at the ranges you wish to shoot, and if there are issues the chrony can be a good tool to diagnose them...
     

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    Last edited: Nov 12, 2013
  4. snojnke

    snojnke Active Member

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    Let's assume that the reloading aspect is spot on. The gun shoots half minute of angle for sure to 600 yards and recently I have been smacking 24" 1640 yard gong without a problem. Playing with my ballistic calculator I just notice that 50fps makes a huge difference. With that said what would be the most acceptable difference in velocities you could expect out of a string of shots?
     
  5. varmintH8R

    varmintH8R Well-Known Member

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    From what I see, most guys are trying to get low teens ES, assuming little or no chrony error.
     
  6. snojnke

    snojnke Active Member

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    Thank you! So would taking an average of the velocities as part of the solution give the most accurate drops then?
     
  7. varmintH8R

    varmintH8R Well-Known Member

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    Take the average as your starting point, and then adjust based on your experience.