Cold Bore Accuracy . . . Development

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by lckytylr, Mar 25, 2015.


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  1. lckytylr

    lckytylr Well-Known Member

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    Dec 30, 2012
    Hello Guys / Gals,

    Can we please start a discussion regarding Cold Bore Accuracy and the process of figuring out what to do and how to do it?

    I'm a Hunter, not a BR guy, so groups are cool, but in my mind, my first bullet is as important as my first and only arrow. With a bow, nothing heats up and it POI really doesn't change, and I'd very rarely get a follow-up shot opportunity, so for all intensive purposes, what happens with that first shot either fills the freezer or leaves an animal to suffer and me with a very guilty conscience . . . thus, I focus ALL of my efforts towards Perfection On One!

    So, can someone please explain the theory behind cold bore accuracy, and then, your specific steps towards figuring it out. Is this something that's done at 100 yds, or at all ranges? Can it be done in the summer (early morning hours)? Can it / should it be done if there are other variables present (wind / moisture / thermals / etc)? I would assume that it should be done only at intended-elevation for hunting location . . . ? Can you get a basis for cold bore accuracy at lower elevations and then fine-tune it up in the mtns?

    Thanks everyone.
     
  2. wbm

    wbm Well-Known Member

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    Dec 18, 2008
  3. MMERSS

    MMERSS Well-Known Member

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    Feb 5, 2013
    Accuracy is placing a bullet, or the center of a group, on the intended target. Cold bore accuracy is not potential group size, this is cold bore precision. Cold bore accuracy does not require a perfectly centered shot on the intended target only a requirement to hit a specific sized target.

    An example for big game hunting. Assume a 10” square or circular target is used to mirror the vital size of a broadside stationary big game animal. A cold bore accurate shot can hit the 10” target in any location with pending results assumed a clean kill regardless of where the target is hit. Any shot outside the 10” target may result in unwanted results and should be considered a non-accurately placed shot.
    I estimate cold bore accuracy in two parts, first what I “DO” know and second what I “DO NOT” know. The second is often the most important.

    “DO” knows

    Cold bore precision potential. This is established by shooting cold bore shots during practice from different firing platforms allowing the barrel to cool between shots. This is not successive fire group potential but rather cold bore precision potential. I may be able to shoot .5MOA cold bore groups on a calm day from a solid bipod with rest. I may only be able to shoot 1MOA cold bore groups on a calm day from an alternative rest such as a backpack without rear bag support. I note the precision potential from each type of shooting platform.

    MV SD. A chronograph can be used to record the MV of cold bore shots with the average velocity and SD noted.

    Atmosphere conditions such as absolute pressure, temperature and humidity. These can be measured with a calibrated weather station such as a Kestrel.

    Spin Drift. Ballistics computers can calculate SD corrections.

    Scope tracking and alignment. This is verified by conducting a tall target test.
    Ballistics calibration. Calibration or truing is conducted to establish calibrated muzzle velocity and range cards/ballistics drag profiles.

    The size of vitals of the game animal hunted. 10” was used in this example.

    Range to target or animal. A good range finder properly used provides this information.

    “DON’T” knows
    THE WIND- estimating how the wind will be acting the entire path of the bullet is often the predominant factor causing a miss. We are all human and can only estimate within a certain degree the average intensity and direction the wind will be blowing when the shot is taken. What we can do is estimate the uncertainty or variable of the wind and try to make the shot as close to this estimation as possible. An average wind speed and direction can be corrected for with variances noted. For example, assume hunting on a flat with the wind predominantly blowing from 3 o’clock. A Kestrel can be used to measure the variance. Look at the Kestrel readings. If the readings fluctuate between 4 and 10 MPH I will assume a 7 MPH average with a plus or minus 3 MPH uncertainty. I will make certain to adjust my range to ensure this uncertainty still leaves room for the bullet to strike the intended target. I “DO NOT” know the exact behavior of the wind but I can apply wind uncertainties to ensure the bullet still strikes the vitals.

    I now use Applied Ballistics Analytics to enter the “DO” knows listed above with the “DO NOT” knows listed below with corresponding range. The solver will predict a cold bore accuracy shot percentage based on this information. The solver may predict a 75% chance of hit. Assuming a hunter is using the guideline “9 shots out of 10” centering the vitals as go/no-go criteria for the shot, the 75% estimate indicates the corresponding range is too far for the current conditions. The solver will additionally list the range for 90% certainty and so on. I use the solver to color code range percentage estimates on range cards. This way if I’m hunting and have a shooting platform providing 1 MOA precision potential with 2 MPH crosswind uncertainty I have a MAXIMUM EFFECTIVE RANGE (MER) annotated for the current estimated conditions and ensure I am not shooting past this range.

    MER parallels cold bore accuracy, ensuring a shot can be made with ensuing certainty to hit the intended sized vitals under the current environment.
     
  4. Mikecr

    Mikecr Well-Known Member

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    I like MMERS understanding of capabilites.
    Once you actually test guns for this, no more wallet groups, just brutal truths w/regard to field capabilities, that's when shooting for you will change completely.

    You'll eventually find great hot grouping guns that are not suitable for hunting, and poor hot grouping guns that are very accurate for hunting.
    With this perspective you start looking at guns that are field practical, and hope they're accurate, or that you can make them accurate.
    When you hit on it, again it changes your shooting, and your hunting.
     
  5. SabreCross

    SabreCross Well-Known Member

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    Mar 14, 2015
    Keep your copper fouling in your barrel but clean out the powder fouling.

    Youtube- "sniper 101 part 40" I do this with all my bolt actions and it works great!