Accuracy /Chronograph

Discussion in 'The Ammo & Reloading Forum' started by .308 shooter, Sep 14, 2008.

  1. .308 shooter

    .308 shooter New Member

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    I posted a thread with the results of my first couple of reload batches. The results were pretty good. But I received a few comments in the way of..."that's great, now wait til you chrono them and see what you get into." or something along those lines.

    My question is this.... What's the purpose of using the chrono is you've found a recipe that works for your rifle? I know it will give you the speed, but why would that matter if you're getting the results you want?

    2nd question. If you found a recipe for one load at one distance, is the formula going to change for futher distances? I know if your shooting a lower velocity the drop could be more significant, but would that affect the accuracy if you've sighted in for the longer range shots? I'm referring to 300 yds or greater.
  2. artabr

    artabr New Member

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    IMHO, the use of a chronograph after you've found your load can be a great help. You can record the effects of climate change on your load, warmer temps increase pressure which increase bullet speed.
    Depending on the chrono you have, you can record load consistency, ie, extreme spread and shot deviation.
    Some chronos such as my Pact have a ballistics calculator which comes in handy.
    If you do think about getting a chrono, think about getting one with a printer.

    I'm not a long range shooter, but I think once you get out to 5-600 yards you'll start to see changes. From what I understand you need speed and weight to fight drop and drift.
    Check the 600 / 1000 yard forum at :

    http://benchrest.com/forums


    Art
  3. knothead

    knothead New Member

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    besides what art said, a chrono will also tell you if your loads are approaching or over max pressure. if bullet velocity is over whats listed in load book ,pressure also likely on the high side
  4. 312shooter

    312shooter Active Member

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    The use of a plain old chrony for 99 bucks immediately sited that reloading data is an "overall approach" to me and I found several powder loads that performed way too hot from what the data showed - in my particular firearm. I was 3gr below max! Also, I found that using remington primers in some loads allowed me to reduce my powder a full grain and get the same velocity as using a cci primer. Most of all it really does add a fun factor to know your entirely "dialed in."
  5. LDBennett

    LDBennett Well-Known Member

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    I have a chronograph but find I find it not that useful for developing accuracy loads. While it helps to find the max velocity, the statistical numbers based on velocity consistency it calculates bare little indication of which loads will give the best accuracy after highly variable loads have been eliminated.

    Look in any magazine (like "Handloader") where they document these staistics on load performance and more often than not the most accuarte loads do not have the best numbers for consistency between shots. Makes no sense but it is what it is.

    Accuracy reloaders need not search out the maximum velocity as more often than not the best accuracy is well below the max load level for a particular load. Comparing max velocities between your gun/load combination and that acheived by the manual publisher is a meaningless comparison as so many things other than the load level contribute to a guns ability to create velocity in a bullet. Signs of pressure are a much better indicator and not exceeding the max loads listed in the manual is still a better way to approach max velocity loads. It has been the rare occassion that I have found a max load in a manual that showed signs of excessive pressure, all other things done correctly. The one exception in developing loads for over 30 cartridges in 20 years of reloading was 223 in a Browning A-bolt. The reason is not know why that particular gun had to be down loaded to escape high pressure indicators when the same load in other guns did not (???).

    Use a chronograph if you wish. My opinon, and yours may differ, is that it is not all that useful for developing accuracy loads. It can readily be used for other evaluations already mentioned in this thread.

    As for range effecting the accuracy, the whole idea of velocity tuning a rifle is to find the velocity where the bullet leaves the barrel at the point where the barrel is near stationary in is oscillatory sinusoidal motion. Once you find that velocity for that bullet, the bullet should be pretty stable through its flight and it cares not where it intercepts the target, close or far ranges. If the accuracy is maximised at 100 yds it will be maximised at 500 yds. At least that is my experience. Maybe others who regulary shoot at those distances can shed more light on the subject.

    LDBennett
  6. USMC-03

    USMC-03 New Member

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    LD is correct in that velocity (i.e. chronograph use) has no direct bearing on developing an accuracy load.

    In my opinion there are only two advantages of a chronograph. One, to check for consistency in for loading process; consistency, among many other factors, equates to accuracy, especially at extended ranges. Two, making sure that the muzzle velocity is at the minimum level to ensure the bullet will remain super-sonic, and thus stable, out to your intended shooting range.

    Regardless, and this is where I disagree with LD a bit, make sure you test your rounds out to your maximum intended firing distance. When using the correct combination of bullet, twist rate, load, etc., etc, short range accuracy usually means long range accuracy, but not always; verify at full range.
  7. knothead

    knothead New Member

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    I disagree with LD & 03 in that a chrono is useful when developing accurate loads, at least for long range shooting. inconstant velocity causes vertical stringing. that said, its interesting to see what changes of various components does to velocity and how groups are affected. one of the things that makes this hobby so interesting.
  8. .308 shooter

    .308 shooter New Member

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    Thanks guys... your information, as always, is very informative. I don't have access to a chrono at this stage, but may look into one or borrow one in the future.... just for kicks.

    I will definitely be testing my loads at longer distances. I'm joining a local gun club that has a 600 yd range. You have to pass a course for anything over 200 yds, but that'll be fun too.

    Thanks again.
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