Great Cold bore group vs wandering shot strings

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by livetohunt, Jun 10, 2018.

  1. livetohunt

    livetohunt Well-Known Member LRH Team Member

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    Well I got to the range today and started working on my load development for my .300 win mag using 215 hybrids. I started at 72 grains and worked up to 76 in one grain increments with 4 shots for each.

    The weather was off and on Rain and wind up to 15 mph. It was about 55 degrees.

    I initially started shooting shot strings as I normally do with 3 or 4 shots. The first cold bore shot would be very close to where the gun is sighted in. Then one shot would wander, next one would wander further, and the fourth shot would be touching the 3rd shot. Overall it would be 1.5 to 2 MOA.

    After this happened at 72/73/74 grains I decided to do complete cool down between every shot. This gave me about .4” 3 shot groups. For 75 and 76. I didn’t shoot the 77 because very light pressure signs at 76.

    These were all at .04” off lands.

    I am more than happy with the cold bore groupings. But I’m concerned with having to take a follow up shot on an animal and my zero wandering!

    I didnt have such a bad issue with this using the 210 VLD hunting.
     
  2. WeiserBucks

    WeiserBucks Well-Known Member

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    Is this the 1st time it's happened or is it repeatable? Have you double checked all of the fasteners on the rifle and optic ? Factory rifle? We need a little more information to help you out .
     
  3. livetohunt

    livetohunt Well-Known Member LRH Team Member

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    Factory rifle. And this happened with the same results with a different scope two weeks ago. It’s just a model 700 that is bedded. Barrel is free floated.

    My only thoughts were it’s wandering from the heat? Can’t be the scope because I shot the wandering groups then shot the tighter cold bore groups afterwards?
     
  4. WeiserBucks

    WeiserBucks Well-Known Member

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    If it's a sporter or even rem mag contour it could be wandering due to heat . Not much can be done about it at the range other than to fire it slowly. In the field, your 1st shot is always the best shot in my experience. After the 1st shot , either the game is spooked, wounded, or both and my nerves go haywire after the 1st shot on game. If your rifle will shoot to point of aim cold bore, multiple times, I wouldn't be overly concerned.
     
  5. livetohunt

    livetohunt Well-Known Member LRH Team Member

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    That’s kind of what I was thinking but I’m still concerned about a follow up shot. And ya it’s just a rem mag contour, it heats up relatively fast. But I haven’t had these issues with the Berger 210’s.
     
  6. elkaholic

    elkaholic Well-Known Member

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    I would try going back to the 210's temporarily and see if it still holds true.
     
    RockyMtnMT likes this.
  7. livetohunt

    livetohunt Well-Known Member LRH Team Member

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    Ya I have some of them loaded up, that’s not a bad idea. I wouldn’t have enough for hunting season though!

    Thanks rich
     
  8. elkaholic

    elkaholic Well-Known Member

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    If there is no difference between the 2 bullets now, I would go with the heating theory.
     
  9. livetohunt

    livetohunt Well-Known Member LRH Team Member

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    Update. Shot today with both bullets. Here are results.

    6 shots with Berger VLD. Onecold bore, one more cold bore to verify a grouping... after the second cold bore shot I let them fly. Barrel was pretty hot after. I usually try to limit shot strings to 4 shots.

    Second target is 4 shots with the 215 hybrids. I shot a .5” group with cold bore and then 3 shots quickly after. As usual it wanders, then those two group. Oddly this time the 4th shot came back to zero.

    So I verified that the 215’s seem to “wander” due to barrel heat more than the 210’s. My cold bore groups with both are about the same at ~.5”.

    It’s lighter barrel. But I’m still perplexed as to why the distance the grouping wanders so much more
    With the 215s. It’s a little hotter load but still! I also verified my ES thru a chrono and with 6 shots my ES was 24 which I will gladly take while fireforming brass.
     

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  10. Barrelnut

    Barrelnut Well-Known Member

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    My 300 RUM shoots the 210 VLD better than the 215. I don't try to fight that. I live close to sea level and that may be the reason. Berger does recommend a 9 twist for the 215... Could be a combination of the barrel walking and a little less stabilization on the 215.

    The 215 group above has a ton of horizontal in it. That could have been shooter related. I know I do it.... Does it always walk horizontal like that or is it random?
     
  11. livetohunt

    livetohunt Well-Known Member LRH Team Member

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    I shot it 2 months ago sitting in the sun and it was about 20 degrees hotter out and it was perfectly vertical... go figure. It was about .05” horizontal grouping at 73 and 74 grains. Both were about 2” vertical.
     
  12. Iceking02

    Iceking02 Member

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    In a conversation about this very topic it was related to me that this can be a symptom of the original heat-treating of the barrel. The solution to this problem for this particular shooter was to repeat heat-treating of the barrel at the barrel-makers shop and then repeat your load development.