KESTREL AB NEED HELP

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Hello,
So my Kestrel Elite is dead on at 1000. However, the closer I get the more my fire solution is off. At 700 the Kestrel is gives me about 2/10 mill more than I need. At 400 the Kestrel gives me about 4/10 more than I need. At 200 the Kestrel tells me I need 4/10, when I only need 2/10. This discrepancy seems linear as my targets are closer. How Do I fix this?

Thanks,
Bang

 

[Changed]

Hello,
So my Kestrel Elite is dead on at 1000. However, the closer I get the more my fire solution is off. At 700 the Kestrel is gives me about 2/10 mill more than I need. At 400 the Kestrel gives me about 4/10 more than I need. At 200 the Kestrel tells me I need 4/10, when I only need 2/10. This discrepancy seems linear as my targets are closer. How Do I fix this?

Thanks,
Bang

Check your rifle data and scope height. Make sure it’s dead nuts accurate. Shoot the dope at 800 and adjust your bc till the dope matches reality.

Choose a custom drag model if possible.

 

[Dthomas3523]

Check all your inputs such as scope height and bullet length. Make sure they are all correct.

Also, typically, if the discrepancy is linear and all inputs are correct, the issue is like with your zero. Make sure the zero distance is correct. A lot of times the default zero is 109yds (100m).

If the distance is correct, make sure your zero is perfect at the inputted distance. If it is off slightly, make sure the offset is inputted correctly.

 

[BANG...ping]

I will double check all my numbers. But I know my 100 yard zero was dead on balls accurate.

Thanks,
Bang

 

[Dthomas3523]

I will double check all my numbers. But I know my 100 yard zero was dead on balls accurate.

Thanks,
Bang

And make sure it was exactly 100yd with a tape or extremely accurate laser.

Nothing wrong with having say, a 98yd or 102yd zero in the kestrel.

 

[BANG...ping]

And make sure it was exactly 100yd with a tape or extremely accurate laser.

Nothing wrong with having say, a 98yd or 102yd zero in the kestrel.

Got it. Will verify my range distance. But what I do not understand is that my actual DOPE for 200 is .2. Kestrel says .4 (50%). Something is way off. I will re check all the numbers. But I know I was pretty anal when setting up my profile to avoid this problem.

Bang

 

[usafa77]

Can you tell us about the load? I have 4 centerfire rifle in my Kestrel. 2 6.5 (2650 velocity) a .308 2550 velocity and a 7.08 2650 velocity. They all come in at .4 to .5 up all day at 200 yds. Thats at 6000 ft elevation. Seems like that's got to be one fast flat bullet to shoot .2, but my experience is limited to those calibers.

 

[Kestrel Ballistics]

Have you done the Muzzle velocity calibration? That usually sorts out these problems as long as you have not changed the BC from the library number in G1 or 7, Hopefully you are using a custom curve so BC is not an issue.

 

[BANG...ping]

Can you tell us about the load? I have 4 centerfire rifle in my Kestrel. 2 6.5 (2650 velocity) a .308 2550 velocity and a 7.08 2650 velocity. They all come in at .4 to .5 up all day at 200 yds. Thats at 6000 ft elevation. Seems like that's got to be one fast flat bullet to shoot .2, but my experience is limited to those calibers.

6 Creed, 107 SMK ~ 3100.

 

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6 Creed, 107 SMK ~ 3100.
Bang

 

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Kk

Have you done the Muzzle velocity calibration? That usually sorts out these problems as long as you have not changed the BC from the library number in G1 or 7, Hopefully you are using a custom curve so BC is not an issue.

I am not using a custom curve. Just published data from Sierra.
Bang

 

[Dthomas3523]

If all the data is input correctly, then see how much different velocity it adjusts for when using the MV calculator.

 

[bjay]

Sometimes its the true BC affecting dope

 

[BANG...ping]

If all the data is input correctly, then see how much different velocity it adjusts for when using the MV calculator.

But any changes to velocity will affect my longer solutions, which right now are dead on.

Bang

 

[DaveM]

Kk

I am not using a custom curve. Just published data from Sierra.
Bang

This is likely why you’re seeing a discrepancy. Bullet manufacturers numbers are not as reliable as the AB numbers and custom curves.

Truing the muzzle velocity is just the calculator’s way of lining up the ballistic curve with the actual points of impact.

 

[Dthomas3523]

But any changes to velocity will affect my longer solutions, which right now are dead on.

Bang

The idea is to make them all line up. Since you’re using BC and not a custom curve, if all your input data is correct:

Shoot longer distances, 7, 8, 1000.
Adjust BC if needed to make those line up if needed

Shoot at distances 600 and in, tweak velocity to make those line up.

Then go back and tweak BC again if needed to make the further distances line up again.

I’d also suggest ditching the numbers Sierra is giving and either use the g7 or custom curve provided by Applied Ballistics. It’s their software and the numbers they provide from their testing will work better.

Again, the idea is to gather real world data, and then tweak the numbers in the calculator to make it all line up. Don’t get hung up that things will take a little tweaking and be on a sliding scale. I.E. you
Change velocity a little to get the closer ranges to work, and then you have to go back and tweak BC a little to get the further numbers lined up.

General rule of thumb:

<600yds = velocity truing
>600yds = BC truing

When using custom curve, your only option is velocity truing unless you have access to transonic ranges.

I usually gather data out to 1k. I just use the calculator to get me close, then ignore it and write down real data.

I’ll then go back, not at the range and use a custom curve and a g7 profile. I’ll use the data I collected and see which one is easier or lines up better. This far, I’ve had pretty good luck with custom curves.

 

[Dthomas3523]

If you want, provide:

Sight height
Twist rate
Bullet used
Chrono speed
Zero range

Then the real world dope for anything you have out to 1k yds.

I’ll make a profile in my 5700 and let you know what I needed to tweak to make it work.

 

[BANG...ping]

If you want, provide:

Sight height
Twist rate
Bullet used
Chrono speed
Zero range

Then the real world dope for anything you have out to 1k yds.

I’ll make a profile in my 5700 and let you know what I needed to tweak to make it work.

Hey D,
Thanks for the information. I have a bunch of real world data out to 1000. Will post it later tonight. Spending the day with the kids. Thanks.

Bang

 

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Hey Dt here are my numbers,

Sight height 2 3/8
Twist 1:7 rh
Bullet 6 mm 107 SMK
Chrono 3120 (Magnetospeed)
Zero range 100 yards
All bullets, powder, and brass are same respective lots
Shooter - real handsome

Here is my observed range data ( 1800 DA, almost no wind)
200 .4
300 .8
400 1.4
600 2.7
743 4.0
1010 6.6

Here is what my Kestrel tells me (current DA as I write this is 2152)
200 .19
300 .67
400 1.28
600 2.7
743 3.88
1010 6.55

As you can see, my 200 yard Kestrel solution is ~ 50 % off my range test results. I used the . 4 (@ 200) and .8 (@300) in a match the day after I verified my range data and hit . 8 MOA KYL targets at 200 and 300. So I know that my DOPE is on. Why does my Kestrel provide accurate solutions at distance, but is off under 400? How do I true my under 400 numbers without affecting my longer distances?

Thanks,
Bang

 

[Dthomas3523]

I’ll mess with them, but needing .4 for 200 is quite odd. You shouldn’t need to dial up that much for a 6m going over 3k.

 

[Dthomas3523]

I can get it all within .1 pretty quick with 3120fps and a .280 g7 bc.

Except the 200yd. That’s just off. Have you tried dialing .2 and see if it still gets an impact? .4 shouldn’t be needed at 200 and might just be so close it will work with either.

 

[BANG...ping]

I’ll mess with them, but needing .4 for 200 is quite odd. You shouldn’t need to dial up that much for a 6m going over 3k.

. 4 worked for 200 and .8 worked for 300. I hit the smallest targets that were on the KYL racks. I am guessing they were .8, but they were likely smaller (possibly .5). However, I check my DOPE on paper the next time I go to the range for a more exact reading.

Bang

 

[Dthomas3523]

. 4 worked for 200 and .8 worked for 300. I hit the smallest targets that were on the KYL racks. I am guessing they were .8, but they were likely smaller (possibly .5). However, I check my DOPE on paper the next time I go to the range for a more exact reading.

Bang

.8 I can see at 300 as I get .7 with a .280 g7.

.2 for 200 sounds correct. I’d definitely verify on paper. .4 is likely too much and I’m betting you’ll find you hit the kyl rack either because the .5 or .8 was large enough to cover the .2 being off, or you hit the top of the target where the hanger connects.

 

[BANG...ping]

.8 I can see at 300 as I get .7 with a .280 g7.

.2 for 200 sounds correct. I’d definitely verify on paper. .4 is likely too much and I’m betting you’ll find you hit the kyl rack either because the .5 or .8 was large enough to cover the .2 being off, or you hit the top of the target where the hanger connects.

I will check my 200 and 300 on paper this Saturday. Thanks to all for the input.

 

[Dthomas3523]

I will check my 200 and 300 on paper this Saturday. Thanks to all for the input.

No prob man. Let me know how 200 looks on paper.