Roperboy87
Well-Known Member
I didn't shoot paper but on still looks really good like make 3in or hair better. My buddy put a kyl rack like Eric at 591 and the little 2 in steel I hit 5 for 5 so I would guess it shoot pretty tight
Help with velocity numbers
- Thread starter Roperboy87
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windypants
Well-Known Member
I've fought this issue with a couple of rifles and have learned to do the reverse zero method. I input the velocity in my solver (Revic BR 4 in my case) and shoot at mid and long range targets. Mine are 656 and 1077 yards. If both are high or low by the same relative amount, I adjust the zero on my scope to fit. If, say, the midrange is on and the long range is low, I'll true the velocity to the long range target and then have to adjust zero to get both on again. That takes a little tinkering sometimes. I only use the 100 yard target to check the windage zero. I don't care if the elevation is off a little. Also, I've learned that if you true up your drops by changing the BC much, it really makes your wind solutions inaccurate in your solver. My 25 creed/135 Berger has a 2885 velocity but trued up to 2855 fps.
It appears to me that you are changing the one variable that you can measure, velocity.
The whole reason for having a chrono is to measure velocity so it is not a variable anymore.
There are a lot of things going on and I suspect that you may have several small things. BC does change over distance. One BC number does not work for shots beyond 600 yds. I suggest that you take the time to set up and shoot some good paper targets and measure the groups and measure the height difference from the actual to the Kestrel. Without measuring you are guessing.
The whole reason for having a chrono is to measure velocity so it is not a variable anymore.
There are a lot of things going on and I suspect that you may have several small things. BC does change over distance. One BC number does not work for shots beyond 600 yds. I suggest that you take the time to set up and shoot some good paper targets and measure the groups and measure the height difference from the actual to the Kestrel. Without measuring you are guessing.
lancetkenyon
Well-Known Member
With 40.8gr H4350, unless you are running a 30" barrel, I highly doubt you are at 2960fps w. a 135. I bet the 2860 is correct.
I am running 42.4gr H4350 in a 26" 1:7.5" Brux and am at 2986fps w. 135s, BR4 and Lapua 6CM necked up to .257". My other 25CM is a 26" 1:7" Bartlein MOD400BB and running the 133s @ 2974fps w. 42.3gr H4350 and Fed GM210M in Alpha brass. This one took longer to speed up with the harder steel.
What was wind doing at 600 and 1000?
Did you verify your scope is tracking true?
Are you using G1 or G7 BC numbers?
You are dead on at 100? Even 1/4" high will make a difference.
Did you change temps and density altitude in your app?
All rifle and load inputs are correct?
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Roperboy87
Well-Known Member
I'm running 26in barrel 6.5srp Lapua neck down. To get my kestrel to match at 600 had to input 2960 and the g7 bc at a thousand I inputted .320. The zero is pretty close to dead zero here's a picture. Yes I input the pressure temp and humidity in for that as well. Also on the kestrel I captured the live temperature. My rifle info is input right. The scope height is 2.3 in I actually measured it out. Once I inputted that info I actually was able to shoot out to a mile that day.
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marksman1941
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Is it a proven scope you're using? I've had vortex razors and vipers in the past adjust in incorrect increments. I had a viper that turned in 1/2moa clicks when it was marked 1/4, and I had a razor that turned was marked 1/4moa clicks but turned in closer to 1/3moa. At range, that makes perceived elevation change per the turret dramatically different than actual elevation change of the POA.
Roperboy87
Well-Known Member
So I the leupold mark 5 that you see mounted on it is new but I put a proven nightforce NX8 on it and Kahles all the same results. I even had my buddy that own the range shoot just to take me out of the equation
Don't get caught up on the velocity discrepancy. You're correcting every error in the model by changing one thing. It's likely a lot of little errors that all happen to line up the same way, requiring a large correction on the one knob you're turning to account for all of them. Your measured velocity is probably correct within the Labradar's margin of error, you're just making a large correction to fix other errors.
If you're worried about it you could try a CDM if it's available for your bullet and program the sight scale factor in your kestrel.
lancetkenyon
Well-Known Member
Is the zero photo inverted (upside down)? Or are you actually low?
lancetkenyon
Well-Known Member
I am using Litz G7 of .334 for the 135 LRHT.
My 100 yd zero shows 3.0mil at 600.
1800'AMSL & 60°F.
My 100 yd zero shows 3.0mil at 600.
1800'AMSL & 60°F.
Roperboy87
Well-Known Member
They are low
lancetkenyon
Well-Known Member
Using that data (.125" low @ 100), a 95 yard zero puts my load at 3.1mils @ 600 yds.
What are your shooting conditions?
Elevation/pressure, temps, wind direction and speed? Wind can push bullets up depending on direction.
I haven't seen coriolis effect anything measurable at 600 yards.
Roperboy87
Well-Known Member
990 ft wind was coming right to left from 3 o'clock at 8 mph pressure on that day 29.94 75 degree 45 humidity
