Group size vs ES

Discussion in 'Long Range Hunting & Shooting' started by djfergus, Jun 16, 2019.


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  1. WildRose

    WildRose Well-Known Member

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    You're getting good results, I would not change anything other than perhaps shooting again with the same setup when conditions are favorable.

    If you want to stretch it on out and see if your vertical dispersion holds, gets worse/better just for fun that's fine, you'll want to do that anyway at some point.

    Optical chrony's are very temperamental due to lighting conditions so I don't expect great accuracy or consistency from them unless your lighting conditions are pretty well perfect and consistent.

    You can frustrate the hell out of yourself wasting a whole lot of time, ammo, and money chasing minimal ES with them.

    Better to leave it home and just shoot if you can't get good consistent conditions.
     
  2. Greyfox

    Greyfox Well-Known Member

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    Given the whole basis of this discussion is a minimal test of three shots to determine velocity/ES. Whether custom or factory, my experience has been that it frequently takes 100-200 shots to stabilize a new barrel with velocity generally increasing, and ES tightening. Frequent and accurate chronographing with a statistically viable number of shots during this barrel break-in process is important, and, an unreliable chronograph, or even measuring drops at long range(500-1000+ yards) before the barrel is stabilized can often be a fruitless exercise for precision long range work, ultimately requiring rework. It’s the price of entry. I find it’s often neccessary to Use as much as 10-20% of the barrel life to have an “effective” rifle for the balance of its life. Efforts to squeeze the life out of a barrel can many times be a false economy. IMO.
     
  3. Chase723

    Chase723 Well-Known Member

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    This is good advice. I as well have relegated myself to the fact that the first 100 or so rounds will get my load close and get me familiar with the rifle. After that, once it settles down, it seems like every cartridge/bullet has an optimal pressure/velocity node and if you have a good consistent barrel, once you’re in the node, you should have really consistent velocities. I just accept it now and don’t get frustrated.

    If your other loads are around an ES of 10 my presumption is that your reloading practices are very sound. Switch to H1000 or Retumbo and I think you’ll be happy.

    Another thing, if you think your chrono isn’t reliable, just take it out as far as you can and look at your vertical dispersion. If it shoots 1/2 MOA at 100 and your ES is less than 15 then at 500 it should shoot ~ 2.5-3” Group. If your ES is >30 it’ll probably be >4”. If there’s no wind and you trust your shooting capabilities then you should trust that info. If you can push it out to 700, then your group should be <5”. If it’s >7-8” Then your ES is likely >30.
     
  4. jasent

    jasent Well-Known Member

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    Nov 16, 2010
    FWIW the pro chrony has an accuracy of plus or minus 2% in good conditions. Poor conditions coupled with slight missalinement and your accuracy goes out the window. I gave up on the pro chrono and left it on the range. Magneto speed and never look back. Your frustration will be a bad memory
     
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  5. Vol1975

    Vol1975 Well-Known Member

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    Feb 6, 2017
    Lots of things can cause ES spread swings.

    Powder for the caliber, case fill (personally I try to fill the case to full so their is no loose space in the brass), brass thickness and type of brass, types of powder, consistent neck tension, not annealing or not annealing consistent, primer and primer pockets consistence and temperature of the conditions.

    This make reloading the challenge that we enjoy.


    Do your self a favor and if it shoots good at the distance you want don’t chase ES. It will drive you crazy if you have a touch of OCD.
     
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