6.5x284 Norma-pleasently suprised

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by craigf, Nov 4, 2012.

  1. craigf

    craigf Well-Known Member

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    I just had the the chance to run my Cooper through the chrony. The rifle is a model 52, 24" barrel, chambered in 6.5x284 Norma. I have shot this rig out to 1,000yds. The one thing I now know, there is quite the difference from 500yds to 1,000. Anyway, the load I chronograph-ed was 140grn Berger vld's, 51grns 4831sc and a base to ogive of 2.380, which is approximately .01 off the lands. I was hoping the fps would be around 2,850. The five shots were, 2,996 / 2,926/ 2,969/ 2,965/ 2,943, for an average of 2,959. From what I've read, the sweet spot for this cartridge is 2,950, for what it's worth, that also seems to hold true for this rifle as well. Enjoy the outdoors!
     
  2. CogburnR

    CogburnR Well-Known Member

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    Wow, you are lucky! I am lucky to get 2800fps with that load!!
     

  3. craigf

    craigf Well-Known Member

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    Not sure what's up, we also chronographed a savage with a similar load, 50 grns of 4831sc, also with the vld's. ended up in the low 28's with that configuration. I never would have thought it would have been that high, but we used the same chronograph for both rifles.
     
  4. Scot E

    Scot E Well-Known Member

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    Are your field data drops at distance, 500 yards or further, matching what your ballistic app is showing they should be for that velocity and distance? It is hard to see errors in velocity or BC up close but at the further distances you will much easier begin to see if your BC and velocity numbers are correct or not.

    Scot E.
     
  5. craigf

    craigf Well-Known Member

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    I actually did things a bit ass backwards. I got things on track at 500yds, which was 8.5 MOA's up, then played with the velocities on the BC to where 8.5 moa's was right for 500yds, and that was 2950fps. Out to 1,000yds things seemed to drop off a bit more, a full 21 more Moa's to hit steel. So I guess things are working out fairly close between the chronograph and the BC. I try learn something new every time I shoot, and I need to shoot a lot more.
    Craigf
     
  6. Scot E

    Scot E Well-Known Member

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    Bass ackwards can work well sometimes! :)

    Just be sure you are not overlooking a couple things.

    1. Make sure you know your true turret adjustments per click. If those are different than what your app inputs, most likely .25 MOA, then your ballistic program will compensate somewhere to make it up and the way you are doing things it would have to change velocity to make things match.
    2. Make sure you zero distance is exact. This will mess things up downrange as well.
    3. Make sure you have your scope height correct. A small thing but it can mess with numbers.

    Atmospheric conditions and shooting skills aside, you are now left with only velocity and BC as factors that can affect POI. I personally always adjust velocity first and only mess with BC's if nothing else will work.

    Scot E.
     
  7. craigf

    craigf Well-Known Member

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    Scot E,

    That does help, and I believe I had everything you mentioned in 1,2,3 of your feedback. I my response I mentioned BC, (as in ballistic calculator) not to get you confused with Ballistic coefficient. I do have the bullet bc's both g1 and g7. Thanks for the input and feedback. Everything helps.

    Craigf
     
  8. trebark

    trebark Well-Known Member

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    Looks like you've got some continued load development work to do. Your ES/SD is waaaay to large.
     
  9. craigf

    craigf Well-Known Member

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    And I honestly don't understand why. Each were measured on an electronic scale. Once fired Lapua brass, and run through the neck die down 2/3 of the neck. Any input?
    Craigf
     
  10. trebark

    trebark Well-Known Member

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    In order to reduce ES/SD there are several things you can do (in no particular order)...

    Change Primer
    Change Powder Charge
    Change Powder
    Change Seating Depth

    Whatever you do, only change ONE thing at time. That way you can measure the effect of the change.
     
  11. craigf

    craigf Well-Known Member

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    I will give those a try, thanks for the input. Heading to Mo. for deer this week, so it will be after our deer season here in Pa.
    Thanks
    Craigf
     
  12. Greyfox

    Greyfox Well-Known Member

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    I think you need to check your chronograph. Your come up from 500 to 1000 yards is consistent with several 6,5-284 rifles that I have tested with the same 51 gr load of H4831sc load that ran velocities at 2700-2800 FPS. The come up for a velocity of 2960FPS at 1000 ft alt and 50 degrees would be approximately 18 MOA. Your come up of 21 MOA would put you in the 2700-2800 FPS range which is consistent with your load and barrel length. My Cooper 52 with a 26" barrel with 53 gr of H4831sc runs 2950 FPS and has a come up of 17.5 MOA. My Savage with the same load and 24" barrel ihas a come up of 18 MOA. All this assumes that your scope tracks true, and there is no radical difference in your lot of 4831sc. IMHO.