help with kestrel

[Okiegunner]

i am using prime 6.5 creedmoor at the moment. Input mv off the box. Zeroed at 100 right after its was sprinkling. Took 5 shots at 1050 trued mv in kestrel. Several hours later take a shot at 890 and its .3 mils high? i would say maybe 5 degree difference in temp. Using the g7 bc of .289. It's in a kestrel 4500 ab am I missing something?

 

[Redmanss]

Did you confirm the .3 mil with a group or a single shot? If it was only one shot, you may have just shanked it.


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[Okiegunner]

Several shots. Took it back out to 1050 and hit after the correction was made

 

[Okiegunner]

I am new to all of this so I am trying to learn more. I experienced the same thing with 140 rdf bullet that I was loading and watch it happen to several other shooters as well. Saw a post that said bc changes with initial mv. Should I tweak my bc to get on target instead of trueing my mv in my kestrel? Also saw were I can input mv for the current temperature. Should I go out an get mv for several temps?

 

[TheGerman]

Your MV guess was just that, a guess for the time you took the initial shots. Since a few hours passed and you just took 5 shots, at roughly the same time, your data was 'on' for just that point in time. The difference could be you had a decent DA swing, your temp swing was more than you thought as well as your sampling size for corrected MV was far too small. Or, a mix of all 3.

Here's a quick and dirty from JBM. You can see how easily .3MIL can show up assuming your MV guess was correct (I'm willing to bet it was close but not dead on) and temp/DA changes:

Ballistic Coefficient:	0.289 G7	Bullet Weight:	130.0 gr	Caliber	0.264 in
Zero Range:	100 yd	Zero Temperature:	59.0 °F	Zero Altitude:	0.0 ft
Zero Height:	0.00 in	Zero Offset:	0.00 in	Zero Wind Speed:	0.0 mph
Zero Wind Angle:	90 deg
Sight Height:	1.50 in	Sight Offset:	0.00 in	Line Of Sight Angle:	0.0 deg
Cant Angle:	0.0 deg	Wind Speed:	0.0 mph	Wind Angle:	90 deg
Show Drop and Windage Deltas:	No	Windage Correction for Zero Range:	Yes
Drop Units:	1.000 mil	Windage Units:	1.000 mil
Target Relative Drops:	Yes	Round Output to Whole Numbers:	No

	2000 ft	4000 ft	6000 ft	8000 ft
Range (yd)	70 °F	80 °F	90 °F	100 °F	70 °F	80 °F	90 °F	100 °F	70 °F	80 °F	90 °F	100 °F	70 °F	80 °F	90 °F	100 °F	Range (yd)
850	-6.2	-6.2	-6.2	-6.3	-6.1	-6.1	-6.1	-6.1	-5.9	-5.9	-5.9	-5.9	-5.8	-5.8	-5.8	-5.8	850
0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
900	-6.8	-6.8	-6.9	-6.9	-6.6	-6.6	-6.7	-6.7	-6.5	-6.5	-6.5	-6.5	-6.3	-6.3	-6.3	-6.3	900
0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
1050	-8.9	-8.9	-8.9	-8.9	-8.6	-8.6	-8.6	-8.6	-8.3	-8.3	-8.3	-8.3	-8.0	-8.0	-8.1	-8.1	1050
0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Trajectory Data

 

[Okiegunner]

Thanks ill check that out on the computer when i get back to the house. I shot about 100 rounds between that at everything between 400 and 800 with a lot of positional shooting. Wasnt till i went back out to the 890 and 1050 target that i was shooting prone that i noticed it was off.

 

[Okiegunner]

Ok went back out today shot 10 rounds over the magneto. Gave me a mv of 2790 put that in my kestrel. Zeroed at 100 and then went out to 810 (longest i had available) kestrel said 6.08 for elevation. 5.8 was above center and 5.7 was below center. So i trued the velocity in the kestrel with 5.75 mils at 810 yards. Gave me a mv of 2731. Is it really possible to have 60 fps difference from the magneto speed. Been told the bc of 330 on the 140 grain rdf bullets was gtg. Am i wrong to think thats not the case? Im loading 42.6 h4350 50 thousand off the lands. Avg mv was 2790 and Sd was 8.4. 2 rounds at 810 had a vertical of less than .25"

 

[DocUSMCRetired]

Have you double checked what your Sight Scale Factor is?

Have you double checked what your MV Shift for temperature is?

Did you use our tested BC?

Did you remove the aerodynamic jump bias from your zero?

 

[Okiegunner]

I cleared everything out of it and started over. Triple checked all my settings and it seems to be lining up a lot better now. Had to of had something funky in the profile or a setting.

 

[Nik H]

Did you remove the aerodynamic jump bias from your zero?

DOC,

How do you remove the AJ bias?

 

[Okiegunner]

Have you double checked what your Sight Scale Factor is?

Have you double checked what your MV Shift for temperature is?

Did you use our tested BC?

Did you remove the aerodynamic jump bias from your zero?

Do you mean the default zero thats 109 yards? If so im not 100% sure. Its all fixed now and seems to be pretty on from 330 out to 1320. Was shooting low at 700 but that was the only place that was funky.