Scope Dope Issues

[Wolf76]

Need some help with doping the scope. Here's the issue. When I go from 200 to 300 meters, the ballistic calculator said that a 2.25 MOA was needed. Made the adjustment and it hit high. Dropped it down to 2 MoA and it was dead on. So, here's the breakdown of the variables:
300 Win 26" tube
77.9 H1000
Nosler brass
2888 chrono verified ES 13
Alt 780
temp 74
scope height 1.72"
shoots less than 1" groups at 300M
215 berger
using G7 BC

Looking to order the CDS but need to figure this out first. Thank you in advance for the help.

 

[velvetant]

All ballistic programs will get you pretty close, all the ones I have used including applied ballistic that I currently use need to be trued or fine tuned.
My advice is to go shoot the different distances and document everything the best you can and give that info to the turret maker

 

[BallisticsGuy]

Seems to me like you're dealing with .25MOA which is less than an inch at 300yrds and perhaps not as perhaps is more appropriate looking inward. You say your rifle only groups ~MOA yet you're worried about .25MOA vertical variance. You're putting the cart before the horse. If you didn't have the air temp right, or had the barometric pressure wrong by a little or your zero was off by 1 click or there was a decent updraft or if any of a number of much more subtle things happened then you could easily be off that much. It's 1 click. The rifle can't even shoot that well for you to determine it was especially deviant. In addition to the above, every app I've built or used varied among themselves by .3MOA normally.

More testing less worrying about non-issues would be my advice. Hopefully that doesn't sound sarcastic. It should read much more glib than sarcastic.

 

[ShtrRdy]

I think you really need to characterize the drops at further distances before making any changes. In Brian Litz's DVD "Putting Rounds on Target" he does some field demonstration with three different rifles and ends up making velocity correction to the ballistic solver for a couple of them, but only at the longer distances.

 

[Wolf76]

Seems to me like you're dealing with .25MOA which is less than an inch at 300yrds and perhaps not as perhaps is more appropriate looking inward. You say your rifle only groups ~MOA yet you're worried about .25MOA vertical variance. You're putting the cart before the horse. If you didn't have the air temp right, or had the barometric pressure wrong by a little or your zero was off by 1 click or there was a decent updraft or if any of a number of much more subtle things happened then you could easily be off that much. It's 1 click. The rifle can't even shoot that well for you to determine it was especially deviant. In addition to the above, every app I've built or used varied among themselves by .3MOA normally.

More testing less worrying about non-issues would be my advice. Hopefully that doesn't sound sarcastic. It should read much more glib than sarcastic.

I appreciate the advice and wanted to clarify what I wrote. The gun shoots ~.23 moa. Last two groups shot .712" and .932" @300m. It has been shooting this well for a while. That's why an inch off is so bothersome. It also printed 3 shots tightly together at an in high.
So, so I adjust the bc to make the cds correct or what? Sorry for being anal about this.

 

[dfanonymous]

All ballistic programs will get you pretty close, all the ones I have used including applied ballistic that I currently use need to be trued or fine tuned.
My advice is to go shoot the different distances and document everything the best you can and give that info to the turret maker

What he said. ^
A lot of people don't like to believe it, but truing is a thing. Keep records of data and use those as reference to align the real world data with your ballistic solver.

 

[WildRose]

I appreciate the advice and wanted to clarify what I wrote. The gun shoots ~.23 moa. Last two groups shot .712" and .932" @300m. It has been shooting this well for a while. That's why an inch off is so bothersome. It also printed 3 shots tightly together at an in high.
So, so I adjust the bc to make the cds correct or what? Sorry for being anal about this.

An inch at 300 is nothing.

A slight inaccuracy in temperature, velocity, BC, or wind could easily account for it.

An inch at 300yds will still kill a prairie dog stone dead.

I'd be more concerned with verifying your dope a 400 and 600yds but you still have to get all of your inputs exactly correct.

Even powder burn rates can vary considerably with temperature and even seating depth.

 

[Canhunter35]

Double check your distances at 400 and 500. If ur one click high, your zero is off. If they're on, recheck at 450 & 550. If they are on your dope should be close then march your shots out to the distance you want to shoot to, verifying your data. Make sure your density altitude is exact. Changes in shooting temp during the day can easily move it a click. I would guess ur temp is off or ur zero is a click high

 

[Bang4theBuck]

Truing is the way to go, as far as I'm concerned. I was always making corrections to my velocities to find the dope that was accurate at the most known distances. Once I started using custom drag models (Litz), much of the variances I was seeing, along with a need to make all of those adjustments went away. If you can program your solver with a custom drag model for that bullet and velocity, and then true it if need be, you will have a good data set. Remember that a CDS turret will only be spot-on in the exact atmospheric conditions for which you did your development under. It would not take much of an atmospheric condition change to a move a 300M impact by 1", just saying. There is a lot to learn trying for that cutting edge accuracy, but maintaining .25 MOA under all conditions is a whole other level of effort. Hats off to you!

 

[coop2564]

Sound like just a velocity change due to conditions mostly.