Range Report  Accuracy of Ballistics Calculator

akmike

Private
Full Member
Minuteman
Jan 28, 2010
24
33
59
nw washington
Hoping for some help. I did a search but didn't find an answer for my question.

I'm starting to use a new handload in my .308.Shooting a Savage Mdl. 10PC. Running 175 SMK,44.0 Varget,Hornaday match brass and CCI BR2 primers. Zero'd at 100 and have shot at 200 and 300. I've not been able to chrony the loads so I worked backward in JBM. Shot 200 yrds and had to come up .7 mil. I input the bullet and pertinent data but having to guess at the MV. To get the .7 mil drop at 100 it showed the MV at 2450 fps. For 300 yrds the chart showed 1.6 mil drop which is right where is shot this morning.

My question: Does anyone have an idea on how accurate the rest of the chart, out to longer ranges, will be as compared to the small amount of real world data I have?

Hope this makes some sense, Mike
 

lowlight

HMFIC of this Shit
Staff member
Moderator
Supporter
Minuteman
  • Apr 12, 2001
    33,426
    28,457
    Base of the Rockies
    www.snipershide.com
    Re: Accuracy of Ballistics Calculator

    Not very without doing more.

    1. Accurate chronograph is critical, absence of this requires you to develop accurate drop tables by actually shooting.

    2. The rifle, the scope, the bullet / load is a system. The system needs to be calibrated to match the ballistic calculator.

    3. Ballistic calculators are not designed to be anything more than useful predictor mainly around changes in the date & time of your current shot. Blindly they will get you close, but how you define close can be subjective. In order words if you know they will be helpful but not exactly accurate.

    Garbage in, will always result in garbage out, as well, taken a step further incomplete data will yield less than complete solutions.

    There are no free rides, your required to do your part.
     

    rpk762

    Sergeant
    Full Member
    Minuteman
    Feb 17, 2011
    885
    1
    45
    Little town now east of Bismarck
    Re: Accuracy of Ballistics Calculator

    Just like LL said. You will have to get some real word shooting in. I have had to change the bc my program was using apparently the lot I got was slightly different. I kept playing with the numbers until they matched my rifles dope for the temps I had data for.
     

    akmike

    Private
    Full Member
    Minuteman
    Jan 28, 2010
    24
    33
    59
    nw washington
    Re: Accuracy of Ballistics Calculator

    I was hoping different, but as I said, suspected as much.

    I'm shooting a match this weekend and due to lack of funds I couldn't afford to buy the factory rounds I had been shooting. I had the components already and figured if I was going to be able to shoot the match I had to put the load together. I guess I'll use this as an opportunity to try and get some real world data on this load in my rifle.

    Thanks for the input.
     

    akmike

    Private
    Full Member
    Minuteman
    Jan 28, 2010
    24
    33
    59
    nw washington
    Re: Accuracy of Ballistics Calculator

    Thank you Liddy, that is very informative. I will have to reread it a few times to be sure I have a better handle on the whole process but a question came to mind intially. In the first bullet point after the section that starts with "Now what" you mention: "We can systematically modify the program output by shooting long-range with our load, and then adjusting the muzzle velocity or BC input to the program until the program output matches the shooting data. I typically do this at a range of 1000 yards with a .308."
    Are you saying you are taking the data just at 1000 yards or working incrementaly up to 1000 yards. I would assume the latter but wanted to make sure.

    Thanks, Mike
     

    Lindy

    Gunny Sergeant
    Full Member
    Minuteman
    Mar 26, 2003
    4,006
    6
    Rifles Only
    www.arcanamavens.com
    Re: Accuracy of Ballistics Calculator

    You want to do that at the maximum range at which you are sure the bullet is still well supersonic. And that might be further than 1000 yards, or shorter, depending upon the load and the conditions.
     
    D

    Deleted member 10043

    Guest
    Re: Accuracy of Ballistics Calculator

    That is a great article on chrono statistics

    <div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">OK. Now that I have shown two loads with a SD of 19 and 6 must be treated as equal, your favorite chronograph number, ES, is worthless and virtually everyone who has ever cited their magic chrono numbers was statistically misguided; what do you do? Throw the chronograph in the junk heap with the other toys that haven’t panned out? Well… No. The chronograph is a useful tool if used appropriately. Just as there are basic elements to correctly aiming a rifle or operating a lathe, – there are basic techniques required to draw meaningful conclusions from experiments with a chronograph. These techniques come from statistics and require only a simple calculator to check.</div></div>