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Thread: cracking group large sd

  1. #1

    cracking group large sd

    whilst doin load dev on my new rifle , I shot the best group of the test loads but the es was 45fps and the sd was 27.8 fps that's with cci br2 primers and n560 (5.5/284 140 amax) I'm thinking a primer change might reduce the sd and the es , does any one agree ? or any other ideas ?
    cheers

  2. #2
    Strangely my best groups have all occurred when the ES has not been good, why? i dont know but i am not the only one to notice this, most of my shooting buddies have reported similar results while developing loads.

    Ian.

  3. #3
    Quote Originally Posted by Whitebeard View Post
    Strangely my best groups have all occurred when the ES has not been good, why? i dont know but i am not the only one to notice this, most of my shooting buddies have reported similar results while developing loads.

    Ian.
    No your not Ian same thing here, not a big issue with a hunting load but if you want optimum results at long range best to keep the es and sd as low as possible in the single digits preferably. I was getting erratic velocities and standard deviations on a very accurate long range load in a 243. It turned out to be the chronograph that was very sensitive to lighting conditions and moreover alignment and placement of shot through it. I use a level to set it up and shoot through it same every time. Failing that then try swapping a component or sorting brass if that's your thing. Usual practices apply back off 10% and work back up

  4. #4
    The only success I have had in reducing SD is by changing powders. Tried switching primers once, it changed the average velocity a little but made the SD worse.

    You can ask all the basic questions like how accurate are your scales, were the loads anally consistent, are you sure all the neck tensions and seating depths are the same. All questions I'm sure you have already asked yourself already.

    I was loading at the weekend. Using R17 I was getting SD's of over 80. Switched quickly to R15 and it came down to below 20. However, if your groups are good over normal stalking ranges an SD of 45 is not going to be a problem.

    I have only been playing the game for 10 years or so, there will be those who are much more experienced than me.
    So much to learn and so little time left

  5. #5
    I've been loading for a while 6 years or so , I compete fclass and am not too shabby , it's the first time I've come across a large sd large es and s good group , I'm going to try and switch from the br2 to the murons I run in my fclass rig which is basically the same case and see what happens
    cheers guys

  6. #6
    Quote Originally Posted by moose243 View Post
    I've been loading for a while 6 years or so , I compete fclass and am not too shabby , it's the first time I've come across a large sd large es and s good group , I'm going to try and switch from the br2 to the murons I run in my fclass rig which is basically the same case and see what happens
    cheers guys
    Loading for F class is well out of my league.

    Best of luck.
    So much to learn and so little time left

  7. #7
    you'd be surprised , a few shovels of powder rest the bullet on top of the case and tap it home with a rubber hammer , job done check it with a ruler for length �� only use a rubber hammer so I don't damage the pointy bit

  8. #8
    Quote Originally Posted by moose243 View Post
    you'd be surprised , a few shovels of powder rest the bullet on top of the case and tap it home with a rubber hammer , job done check it with a ruler for length �� only use a rubber hammer so I don't damage the pointy bit
    Now you're talking...
    So much to learn and so little time left

  9. #9
    Originally Posted by moose243 you'd be surprised , a few shovels of powder rest the bullet on top of the case and tap it home with a rubber hammer , job done check it with a ruler for length �� only use a rubber hammer so I don't damage the pointy bit

    Now you're talking...

    I second the above....

    There must be a direct relationships in the sales of hand wipes when fps, primers, power measurements and case lengths are mentioned.....


    Tim.243
    Stalking is very much like going to the night club

    You can always tell an Essex Boy, just you cant tell him much...

    An hour in the field is worth a week of typing trash.....




  10. #10
    Quote Originally Posted by gr1ffer View Post
    No your not Ian same thing here, not a big issue with a hunting load but if you want optimum results at long range best to keep the es and sd as low as possible in the single digits preferably. I was getting erratic velocities and standard deviations on a very accurate long range load in a 243. It turned out to be the chronograph that was very sensitive to lighting conditions and moreover alignment and placement of shot through it. I use a level to set it up and shoot through it same every time. Failing that then try swapping a component or sorting brass if that's your thing. Usual practices apply back off 10% and work back up
    I know what you are saying griffer, i have had 6mmBR and 22BR extreme spreads down in single figures and low doubles but it was noticeable that the smallest groups had higher ES, all cases had full BR prep and were sho @ 100yds of a rest on a concrete bench at Minsterly Ranges.
    I have not chronoed my pet 22BR load for a few years now but it still puts five into sub 2" @ 500yds so i presume the ES is staying pretty low.

    Ian.

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