Range Report Need some help from some of you mathematicians

[Mike9685]

Okay -
I've worked up some ballistic tables for my best handloads for my weapons (both 223 and 308, bolt and black rifles; AND, with/without a YHM suppressor - but that's another subject...)

NOW, the range I use does have 100 - 600 yd targets. All are 100 yd intervals. They won't let me setup targets at 25 yd intervals.

When I verify my "come-ups", IS THERE A FORMULA FOR INTERPOLATING the differences in computed data vs actual data so I can break it down to 25 yd segments? In other words; if I'm right on at 100 yds, but I'm 1" low at 300 yds <span style="font-weight: bold">(from computed data)</span>, what's the formula for computing POI at 150 yds, 175 yds, 200 yds, 225 yds, 250 yds, 275 yds, etc? I've tried "tweaking" the software (DA, temp, etc.), but I'm more like a hog looking at a wristwatch...I can get the data for 100 - 600 yds (actual verification firing), but how do I compute the corrected data, say (ie) from 400 and 500 yds so I know the come-ups at 425, 450, and 475 with the actual firing data at 400 and 500 yds? Hope I'm clear...

ANY help would be appreciated.
Mike

 

[Bevan]

Re: Need some help from some of you mathematicians

Do your actual comeups at 200,300,400,500,600 whatever match what the computer says? what data do you have?


If they don't match, use JBM, set atmospherics etc as close to what you were shooting in as possible, use LITZ bc for your bullet, then adjust muzzle velocity field until program comeups match your field data

there are problems with doing this such as scopes that don't track correctly etc, atmospherics entered incorrectly into the program, angles not corrected for, shooter error etc.

 

[George63]

Re: Need some help from some of you mathematicians

for that small of adjustments the ballistic program is likely over kill

lets say if you are 8 clicks between 200 and 300 of course just divide it evenly, between 300 and 400 lets say you are 14 clicks, half would be 7 but the drop will be more from 350-400 than from 300-350 so for 350 you would go 6 up from 300 and 375 would be 9 or 10 up from 300, at the point of 1 click difference you are really splitting hairs, in the field what is the chance of estimating range that accurately?

 

[Bevan]

Re: Need some help from some of you mathematicians

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: George63</div><div class="ubbcode-body"> in the field what is the chance of estimating range that accurately? </div></div>


About 100% if you have a laser



I find JBM ballistic calc when used properly to be pretty much dead on, took my paper chart to 820 meters (just over 900 yards) today, chrono'd MV and Litz BC, elevation dead on (or as close I can hold ) the whole way out


If you're getting erroneous results you've got a bad input?

 

[Greg Langelius *]

Re: Need some help from some of you mathematicians

I only use computation for limited purposes.

I use it to estabish <span style="font-style: italic">ballpark</span> drops and drifts when inaugurating a new load and/or rifle, so I can have some semblence of a reasonable POA at my starting distances. I trust the calcs to get me onto the paper, but for little, if anything, any more precise.

Once I have found my actual drops, I tweak the spreadsheet so the calculated trajectory approximates the actual as closely as possible.

At this point, the environmental data is verified, and that spreadsheet is considered relatively reliable, <span style="font-style: italic">but only for those particular environmental conditions</span>.

Subsequently, a 'working copy' of the spreadsheet is altered to refect actual, current environmental conditions, and the resulting dope is compared against the original spreadsheet so I can anticipate <span style="font-style: italic">trends</span> where the POI shifts correspond to the environmental changes. After action, the actual results are edited into that spreadsheet.

At no time do I rely upon computations to provide a shooting solution. To my mind, thats putting the cart ahead of the horse.

The working spreadsheets are saved after their data has been confirmed to correpond to real performance under different given sets of conditions.

This is my way of maintaining a 'data book'. Their truest value is to teach me, and remind me, about how my rifle performs; and not as a means to predict and dictate shooting solutions. The problems inherent in that approach are because most shooters personal performance cannot duplicate the precision a computation claims to deliver, at which point the 'truth' is not in the calc, but in the real performance.

Additionally, per the "Garbage in..., garbage out..." dictum; computations are only as good as the data you input. In reality, the best data a human can provide is incomplete and only coarsely accurate. Accordingly, output data can only be incomplete and coarsely accurate

Moreover, by the time data has been entered and crunched, conditions have proabably changed enough to make them only a rough estimate. In essence, the output is aready history by the time it emerges.

I seriously mistrust data and computations as a means to predict and establish shooting solutions. I base this on the eexperience of a lifelong career in computer operations and programming.

The ways to improve on it involve SWAGs, or Scientific Wild-Assed Guesses. I.e., "the table says 'X' amount of windage, and my gut says the wind estimation error is to the left (or right...), so i will hold off slightly, about half of my guess, into my supposed wind difference.

You 'hedge the bet'. Sometimes you get it right, and sometimes the bear eats <span style="font-style: italic">you</span> instead. For either eventuality, learning is (or at least should be) occurring.

Greg

 

[Mike9685]

Re: Need some help from some of you mathematicians

Thanks Guys...
I guess I was "over thinking" this. I was trying to workup "Come-ups" for 5 different rifles, 2 different calibers, both with and without the POI shift for the suppressor. I don't think I can afford the time and $ to verify all the combinations...Guess I need to concentrate on 1 in each caliber, with/without the suppressor.

Greg - I used a SWAG all the time I was flying Cobras...also TLAR (That Looks About Right) and TFAR (That Feels About Right). You're right...sometimes you get the bear, and sometimes the bear gets you...still feel bad about that new latrine...freshly painted and remodeled...must've been the crosswind...

Mike

 

[sniperaviator]

Re: Need some help from some of you mathematicians

The easy way is to go half way and round it down.

Another more accurate way to estimate it is to do this. Lets say you want to interpolate for 1550 yards, and you have data for every 100 yards. Take the data point for 1400 yards and 1600 yards. Now subtract and divide by two (the mean). Now take a look at the data for 1500 yards. Lets say it is 10% lower than the mean. So, go 10% lower than the mean for your 1550 yards.

Since the trajectory curve is a quadratic equation, you could ESTIMATE it by taking the square root of the difference in moa (or mils) for 1500 yards and 1600 yards.

EXAMPLE:
1500 yards 30moa
1600 yards 40moa

40-30 = 10
sq root of 10 = 3.16
1550 yards 33.16

None of these are totally accurate. What I did once was GRAPH my distance vs moa. Then you can interpolate on the graph.