S&B click values, 250gr Lapua Scenar - cannot find ballistic solution

338TRG42

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Minuteman
May 26, 2014
2
0
I shoot a 338 Lapua - TRG 42. The rifle is a dream - shooting half MOA and better on 1000m.

I need help on the following two issues:

1.)
1-10 Twist
250gr Lapua Scenar
880m/s
834hpa (absolute)
Zeroed at 200m
MRAD clicks (S&B 5-25x56 - first focal plane)
Shooting north south in order to (almost) eliminate Coriolis from the equation.

My actual clicks:

400m - 13 clicks up
650m - 37 clicks up
1000m - 80 clicks up

I have tried two different ballistic programs (Shooter App and Strelok Pro). Both give me 14 click up at 400m and about 74-75 clicks up at 1000m. I am irritated by the 5-6 clicks (50-60cm) out at 1000m. So I have too little clicks at 400m and too many clicks at 1000m.

The only way I could match that curve out to 1000m is by increasing the speed to from 880m/s to 910m/s and decreasing the G7 BC from 0.322 to 0.24 on the program. However both values are not realistic and I would like to get the clicks past 1000m. I just tested the rifle at 1350m. The bullet landed about 10meters (!!!) higher than it should according to the program. This is due to the fact that the BC was brought down so much.

The only way I can explain that to myself is that the scope does not click as it should - the clicks closer to the zero are larger than 1cm/100m and the further you get away the smaller they get. Can that be?

Can anybody help?


2.) I zero my rifle on 1000m in the morning at about 15 degrees Celsius. If I don't change anything, the rifle will shoot about 70-80cm higher at lunch time at about 25 degrees. According to my ballistic program the shift in POI cannot shift that much. At lunch time there is always a little mirage. How much can mirage actually do the the POI? What other factors can cause the shift in POI? Would a mirage band help?

Thanks for your help.
 

lte82

Shooter
Full Member
Minuteman
  • Mar 12, 2013
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    What value are you using for scope height (above bore)?
     

    Rob01

    Cool Moderator
    Staff member
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    Minuteman
    Jul 9, 2001
    13,999
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    Stop talking in clicks and speak in the actual value of the scope, mils. Run your data in mils and use the big numbers on the turret to dial to that. The sooner you lose clicks the sooner it will be easier to work the data as you aren;t going to count 80 clicks. You dial right to the 8 mil mark. Simple.

    Ballistic programs are garbage in and garbage out. Make sure you have all the right numbers going in. .5 mils off at 1000 yards is a good amount but can happen as not all calculators are right on. It's to get you close which it did.

    As for the scope, run a tracking test on it out to atleast 10 mils and see if it is tracking properly.
     

    Redmanss

    8541
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    Minuteman
    Aug 24, 2010
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    Northeast Wyoming
    ^^What he said! Also, have you run your loads through a chronograph to confirm MV? Confirm your speed before you start adjusting your BCs. What are you using for your climate inputs?

    It really sounds like there is something wrong with your inputs, but test the scope first at close distance (100m).

    Mirage can have an effect, but usually not as significant as you're seeing unless it's really heavy. Dial down the magnification to reduce that effect.
     

    338TRG42

    Private
    Minuteman
    May 26, 2014
    2
    0
    Thanks guys for your input so far.

    Clicks on my scope = 10 * Mils -I am not confused with this.

    I am using 5.2cm of scope above bore - I measured centre bore to centre scope. Is that correct?

    Climate input: Absolute air pressure; temperature; humidity

    The tracking test is on my to-do list for the next shooting range session.

    I ran my loads over two different chronographs. If the MV was out, I would always have too many or always too few clicks.

    Frustrating to say the least.....
     

    JBNj

    Sergeant
    Full Member
    Minuteman
    Aug 1, 2013
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    Central Jersey
    Did you know the shooter app has a velocity calibration input based off shooting multiple distances and scope adjustment. Before getting frustrated give that a shot. I checked on the shooter app and it calibrated to your actuals so.....