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Kestrel and Horus dope

Sako man

Sako man

profesional dilettante
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Minuteman
    • Sep 7, 2012
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    3,049
    Galactic Sector ZZ9 Alpha Xray Plural.
    Ok, so here goes another post that actually started it's life as a question on scope tracking. I have now done tracking tests and found the optics to be accurate and track spot on. So I know this is not the issue.

    <span style="font-weight: bold">The issue:</span> I enter my ballistic data into the Kestrel with Horus on 175 smk traveling at average of 2684 with a BC of 496. The Kestrel then says dial 14.1 mills and I end up actually having to dial 14.9 mils before hitting steal. This is at 1180 yards. So there is a discrepancy in what the software is saying and what I am actually having to dial.

    I know my optics track perfect. I know my average MV is accurate as I chrono it that day and time. The thing I am thinking is that the 496 BC is not accurate?

    Many of you have said "test things out" and I have. But still scratching my head. The bullet is not lying so I have to change some input variables on the software side I think. Keep in mind that the Kestrel is getting real time data on Baro, DenAltitude, etc.. so that stuff should be accurate. Am I missing any important input variables perhaps?

    Ideas and advice appreciated.

    Thanks

    Tuber




     
    Re: Kestrel and Horus dope

    If you have all the variables that were entered, including weather from the kestrel post it and others can run it and see what they get compared to the Horus ballistics.

    So list the details used.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jon Lester</div><div class="ubbcode-body">How sure are you on the 2684? </div></div>

    Ok, well I chronoed those rounds/load that day within an hour of getting out to steal. And I did the chrono at the same location.

    I used a magnetic chrono which is 99.6% to 99.9 accurate.

    http://www.magnetospeed.com/pages/reviews-tests

    So I think that the MV was accurate.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">If you have all the variables that were entered, including weather from the kestrel post it and others can run it and see what they get compared to the Horus ballistics.

    So list the details used.

    </div></div>

    .308
    175 Nosler sorry not SMK but same posted BC and profile as SMK I believe?
    496 BC
    MV 2684 Avg
    11.25 Right H twist
    Zero range 100 yar
    Seat height 2.4"
    Angle to target -2.0 deg
    Alt 467
    Density Alt 1150 feet
    Pressure 29.9 HG
    Humidity 50%
    Temp 58F

    Distance to ispc: 1170yard to be exact (not 1180). And Horus Kestrel data was telling me dial 14.1 mils. Dialed 14.8-9 and that got me to 0 at that dist.

    It will be interesting to see what people get.
     
    Re: Kestrel and Horus dope

    So are you shooting SMKs or Noslers? Either way Ballistic AE out puts Noslers at 13.9 and SMKs at 14.3.

    What kind of rifle are you shooting, the 2.4" sight height sounds way tall IMO.
     
    Re: Kestrel and Horus dope

    For whats it worth...

    I just ran it again in cold bore and it outputted 14.9
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BigJohn141</div><div class="ubbcode-body">So are you shooting SMKs or Noslers? Either way Ballistic AE out puts Noslers at 13.9 and SMKs at 14.3.

    What kind of rifle are you shooting, the 2.4" sight height sounds way tall IMO. </div></div>

    Yes, it is tall. It's an AI mount an an AX chassis. The mount has to be pretty high as there are clearance issues with the AX.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BigJohn141</div><div class="ubbcode-body">For whats it worth...

    I just ran it again in cold bore and it outputted 14.9 </div></div>

    Wonder why the Kestrel is telling me 14.1? So it's interesting that you came up with the correct dope that actually worked? Wonder if I have a screwy setting?
     
    Re: Kestrel and Horus dope

    Both ballistic AE and cold bore are listing both bullets with a BC of .505

    I actually forgot to set the sight height and after I did it put it down to 14.3-4 range. When you are talking over 1000, a lot of little things can and will make a BIG difference.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BigJohn141</div><div class="ubbcode-body">Both ballistic AE and cold bore are listing both bullets with a BC of .505

    I actually forgot to set the sight height and after I did it put it down to 14.3-4 range. When you are talking over 1000, a lot of little things can and will make a BIG difference. </div></div>

    The BC1 of either is 505 but that is above 2800 fps. So I used an input of 496.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BigJohn141</div><div class="ubbcode-body">Again, which bullet are you actually using, the SMK or Nosler? </div></div>

    Yeah sorry the Nosler not the SMK. But according to nosler the profile is the same.
     
    Re: Kestrel and Horus dope

    If I plug everything you have exactly into ColdBore,

    175gr
    .496
    2684fps

    Sigh Height 2.4

    59 degrees
    29.9
    50%
    (basically I left it at standard pressure it defaults too, just changed the humidity)

    I get 14.9 for 1170 yards and 15.1 for 1180...

    Point Mass drops the ball again.

    Not all ballistic calculators are created equal and how they handle data is the question.

    I would tell your Horus your sight height is 1.5 and I bet it lines up better for you, as the PM programs I have tried don't get answer right at 2.4. JBM I get close to 14.5 bringing the sight height down lines it up. You could tweak your velocity too, subject like 20fps because most programs figure the distance from the chronograph is 10ft, so since you are at the muzzle, you can just automatically start subtracting 20fps or so ...

    You'll just have to tweak one place or the other and decide which works under the conditions you shoot more time then it doesn't work. The MV would be a good place to start.

    But ColdBore for me is dead on at 14.9 at 1170.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">If I plug everything you have exactly into ColdBore,

    175gr
    .496
    2684fps

    Sigh Height 2.4

    59 degrees
    29.9
    50%
    (basically I left it at standard pressure it defaults too, just changed the humidity)

    I get 14.9 for 1170 yards and 15.1 for 1180...

    Point Mass drops the ball again.

    Not all ballistic calculators are created equal and how they handle data is the question.

    I would tell your Horus your sight height is 1.5 and I bet it lines up better for you, as the PM programs I have tried don't get answer right at 2.4. JBM I get close to 14.5 bringing the sight height down lines it up. You could tweak your velocity too, subject like 20fps because most programs figure the distance from the chronograph is 10ft, so since you are at the muzzle, you can just automatically start subtracting 20fps or so ...

    You'll just have to tweak one place or the other and decide which works under the conditions you shoot more time then it doesn't work. The MV would be a good place to start.

    But ColdBore for me is dead on at 14.9 at 1170. </div></div>

    OK so taking into consideration what you are getting I used the iSnipe app for the iPhone. Was a $5 buck download. Plug in my info and whamo! I get 14.84 mils at 1170. I don't know if there is something important I am missing with the Kestrel but if a $5 dollar app can get it right then why not a $600 piece of hardware?

    But as you say I will start with MV as it's an obvious culprit and see where to go from there. As well I should look into Coldbore for fun.

    What is a good recommendation for hand held/field firing solutions?

    Lastly, Horus is literally a mile away from my office so I may got over there and bug them a little to see if it's possible that I am not using the hardware correctly "this is highly possible"

    Thanks for the research!
     
    Re: Kestrel and Horus dope

    I just plugged the data into my kestrel with what you gave. I never used those Noslers before, so I just used BC .475 that is close to SMK for input data. With the environmental data turned off, input your data readings, adjusted the BC to .475 (Litz's), I am getting 15 mils.

    When I go into the true function with your data, to match your correct elevation hold, I adjusted the MV to 2693.

    It's your MV and BC that are not matching up. Any other data for targets that day?

    By the kestrel, you are subsonic at 1170 yards.
     
    Re: Kestrel and Horus dope

    I've been thinking of getting a less expensive Kestrel that gives me DA and then using a iPhone app to calculate external ballistics. From some of this discussion it sounds like a good way to go to save a few hundred bucks.
     
    Re: Kestrel and Horus dope

    How do you know your scope tracks correctly? I'm not being a jerk i'm just asking. Did you measure with a laser bore site, or did you shoot to test this? The only way that is truly dead on is by using a laser, it eliminates the human factor. Just a thought / suggestion.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Smsnipes</div><div class="ubbcode-body">How do you know your scope tracks correctly? I'm not being a jerk i'm just asking. Did you measure with a laser bore site, or did you shoot to test this? The only way that is truly dead on is by using a laser, it eliminates the human factor. Just a thought / suggestion. </div></div>

    It's a valid question for sure.

    I did tracking tests on my Leupold and Premier. Both tracked great. The tracking test consisted of punching holes every mil at 100yards on a large piece of cardboard. So it was an extensive enough test to tell me for sure the accuracy of the tracking.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 8up</div><div class="ubbcode-body">I just plugged the data into my kestrel with what you gave. I never used those Noslers before, so I just used BC .475 that is close to SMK for input data. With the environmental data turned off, input your data readings, adjusted the BC to .475 (Litz's), I am getting 15 mils.

    When I go into the true function with your data, to match your correct elevation hold, I adjusted the MV to 2693.

    It's your MV and BC that are not matching up. Any other data for targets that day?

    By the kestrel, you are subsonic at 1170 yards. </div></div>

    Where are you getting 475 as the BC for 175 SMK? All I can find on the box and the net is that the BC of both the Noslers and SMks is 496.

    Perhaps this is a question for Brain Litz?
     
    Re: Kestrel and Horus dope

    With the bullet library I have with shooter app on my phone, Litz's number for 175 SMK is .475, I believe it is in his book. I don't have his book but I need to get it. I use his numbers for all my data in the kestrel and they are on.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 8up</div><div class="ubbcode-body">With the bullet library I have with shooter app on my phone, Litz's number for 175 SMK is .475, I believe it is in his book. I don't have his book but I need to get it. I use his numbers for all my data in the kestrel and they are on.

    </div></div>

    Interesting. I will use 475 for input and see what the Kestrel says. Wonder what the discrepancy is between Litzs calculations and what the companies are printing?
     
    Re: Kestrel and Horus dope

    Bryan has created a new "average" for the BC.

    For a company the higher the bc they publish, the better it is for sales.

    Most of those, I believe they average for around 3000fps which nobody gets out of their 308s. So you have to offset it.

    The factory bc is .505, the long time average has been .496 and now Bryan has determined that .475 is a better solution. He is probably running it closer to what people actually shoot it at.

    BC are NOT set in stone, they move based on the speed of the bullet. Which is why "banding" works better, when you tell the computer to adjust. JBM will band the bullet if you pick the non-litz numbers. They give you three values based on various MVs for the bullet's flight.

    Bryan averages these, which helps with a one number solution.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Bryan has created a new "average" for the BC.

    For a company the higher the bc they publish, the better it is for sales.

    Most of those, I believe they average for around 3000fps which nobody gets out of their 308s. So you have to offset it.

    The factory bc is .505, the long time average has been .496 and now Bryan has determined that .475 is a better solution. He is probably running it closer to what people actually shoot it at.

    BC are NOT set in stone, they move based on the speed of the bullet. Which is why "banding" works better, when you tell the computer to adjust. JBM will band the bullet if you pick the non-litz numbers. They give you three values based on various MVs for the bullet's flight.

    Bryan averages these, which helps with a one number solution. </div></div>

    .475 is right on the money. Nice!

    Just ordered some berger 175 tactical, advertised bc of .510, but if Litz publishes that stated bc I would believe it.
     
    Re: Kestrel and Horus dope

    sorry to drag just slightly off topic, but when determining "sight height" is it a measurement in inches from the mid point of the action to the mid point of your scope? I just read LL's post about plugging in 2.4 for this input, but I always had mine as 1.5 or 1.75. Curious if I have been entering bad data? Thanks.
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FALex</div><div class="ubbcode-body">sorry to drag just slightly off topic, but when determining "sight height" is it a measurement in inches from the mid point of the action to the mid point of your scope? I just read LL's post about plugging in 2.4 for this input, but I always had mine as 1.5 or 1.75. Curious if I have been entering bad data? Thanks. </div></div>

    Did you measure? What is your actually seat height? But yes it's quite possible/probable that you have been using errant data if you were not measuring bore height to center tube on your optic.

    My setup is high as I am using a high mount and have to make clearance for a 56mm objective and rail system on an AX chassis.
     
    Re: Kestrel and Horus dope

    yes, I measured. I went from the center axis of my action to the mid point of my scope. I got right at 1.75", but seeing LL's number, I thought I might be wrong...seemed tall to me. I am curious now how much that could throw one's dope off it were, say a half inch too tall? Thanks for the help. And again, sorry to take your thread to another planet!
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FALex</div><div class="ubbcode-body">yes, I measured. I went from the center axis of my action to the mid point of my scope. I got right at 1.75", but seeing LL's number, I thought I might be wrong...seemed tall to me. I am curious now how much that could throw one's dope off it were, say a half inch too tall? Thanks for the help. And again, sorry to take your thread to another planet! </div></div>

    The thread is really about data and (seat height) feeds into that context.

    I have tried various seat height inputs and indeed it does throw calculations enough to count at distance.
     
    Re: Kestrel and Horus dope

    I have used a lot of programs and never had one be perfect without tweaking something. I shoot, gather data and adjust speed and bc until the numbers match. I have never had one as close to perfect as my Horus is....I love it! Sorry to hear your having issues..
     
    Re: Kestrel and Horus dope

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: heatseekins</div><div class="ubbcode-body"> I have used a lot of programs and never had one be perfect without tweaking something. I shoot, gather data and adjust speed and bc until the numbers match. I have never had one as close to perfect as my Horus is....I love it! Sorry to hear your having issues.. </div></div>

    The trouble I think is on my end. Bad data in, bad data out. It's only as accurate as the info I feed it. Good news is once I fed it .475 BC things started to line up nicely.

    p.s. I have three sets of Seekins precision rings, they are the only rings I prefer to use when I can. A quality precision product sir.
     
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