I am new to long-range shooting.

I am curious to know what you all use as input variables for calculating your drop chart on any given day/atmospheric condition to make a first round hit at long-range?

What are the bare minimum inputs a person needs to get an accurate solution for a first round hit?

I have a kestrel 2500 which will give me pressure, altitude, temperature and wind speed. I use this in conjunction with "Shooter" app for the iPhone. However, it doesn't give me accurate data to have first round hits out at 700 yds and beyond. Once I "true" the velocity it works great but I want to figure out how to get first round hits at distance without having to true the velocity every time I got out to shoot. Most people I have talked to said to adjust my velocity to make the drop table work, however, I can't know how much to adjust velocity to make the drop table work if I don't know where I am hitting...

How many of you use Density Altitude?

Sorry if this post seems to be frazzled and all over the board. I am trying to make sense of this all, especially since every time I go out to shoot the atmospheric conditions are different so what worked one day will not work the next day. How do I overcome this?

Others with more experience will chime in I am sure, but my gut feel and limited experience suggests that computers by themselves will not give the answer. They will get you close, but for a first round hit the solution they give must be verified by empirical evidence ie. testing.
By first round hit, what size target are you talking about? At 700 yards I would think that you are talking about a 7 inch bullseye, with perhaps a larger aiming point.
The Tracking Point system may have achieved better results but I can't remember.
Just my 2 cents.
Peter.

quote:

Originally posted by Peter:
Others with more experience will chime in I am sure, but my gut feel and limited experience suggests that computers by themselves will not give the answer. They will get you close, but for a first round hit the solution they give must be verified by empirical evidence ie. testing.
By first round hit, what size target are you talking about? At 700 yards I would think that you are talking about a 7 inch bullseye, with perhaps a larger aiming point.
The Tracking Point system may have achieved better results but I can't remember.
Just my 2 cents.
Peter.

Are you having trouble with elevation or windage? Elevation should not be too of a problem, unless you are shooting ball powders in temperatures that vary a lot.

I use a BR2, which I find to be incredibly accurate. However, if you think all you have to do is hold your Kestrel in the air and measure the wind, you are probably going to be disappointed. I went out coyote hunting yesterday but threw my 7 STW in the truck. At mid day I went to a place where I have a rock at 700 yards painted black with a 2 inch orange aiming circle. I measured the wind at 10 mph; that would normally be 4 MOA of wind in STW, but I know from experience that would be at least 5 MOA. The mirage was completely washed out, and bushes were blowing pretty hard. Wind was right to left. I held just inside my 6MOA line and hit 2 inches low and 2 inches left. Shot sitting with my bipod and sling.

I have found the wind is always more than a hand held anemometer would indicate.

I am mostly having trouble with elevation, not windage, even with elevation it only takes me 2 or 3 shots to get that dialed and from that point forward my firing solutions work very well since the app has a function to "true" the data. I just want to learn how to consistently get first round hits in varying conditions.

I am using what I understand to be a very temperature stable and accurate powder, Hodgdon H4350 with 140 gr Hornady Match BTHP bullets. This is out of a .260 Remington.

It seems to me that we have a solid understanding of physics and the atmosphere that computers will indeed output a perfect solution for elevation every time but that can happen only with good input.

Just couple of questions:
Are you using a predicted BC or a measured BC for your bullet?
Are you using G1 or G7 ballistic profiles?
Have you measured your sight height above bore?
Have you measured velocity with more than 1 chronograph?

quote:

Originally posted by Balule:
Just couple of questions:
Are you using a predicted BC or a measured BC for your bullet?
Are you using G1 or G7 ballistic profiles?
Have you measured your sight height above bore?
Have you measured velocity with more than 1 chronograph?

I'm using published BC
I believe it is G1 (I checked when I entered the data but I don't recall off-hand)
I have measured sight height above bore
I've chronoe'd over 2 diff chronographs.

In talking with a few of experienced shooters, they told me they just adjust their velocity to make their table work. That seems to be the only unknown and unpredictable factor. It seems bass ackwards to me to shoot to see where you're going to hit then adjust to make your table work. The whole point is to get a 1st round hit.

Bryan Litz reports variation in manufacturer published BCs of up to 15% in both ways compared to his measured BCs.
Using G1 vs G7 ballistics I ran a simulation through 'Ballistic' for IPad and got a predicted difference in drop of 2.5MOA at 700 yards for my 308 Win load with the Nosler 155CC.
I have had good trajectory prediction in 3 calibres shooting mostly at 2 MOA gongs up to 550 yards with 'Ballistic' and the measured BCs. I have only shot the 308 further and it went true.
Long distance is finicky, I witnessed 2 misses by an excellent shot on a Vaal Rhebuck at 635 yards - the cause was a 0.75 MOA discrepancy in zero. Fortunately the impacts were witnessed and the 3rd shot went true.
Please keep us updated with developments in this regard!

No expert here by any means but what at a minimum you need 1) all the weather info (barometer, humidity, elevation, temp,), bullet info, and actual velocity at the time you sighted in the rifle.
2) all that info at the time you are shooting.
And you really need to check out the actual drop at extended ranges. I have found that my computed drops are usually pretty good out to 600y (longest range I have) but my windage estimation is really bad. What the wind is doing where you are can be off by 180 deg. at halfway to the target. SOftware will get you in the ballpark but it really takes lots of practice.
C.G.B.

Go to gseven.com and use their ballistic calculator. You will have to do some long range shooting to get the data you need to input, and you'll need to measure the atmospheric conditions on the day you shoot. There is a velocity validation feature that should get you real close. The quality of your inputs will determine the quality of your ballistic solutions.

This is the same company that makes the BR2 rangefinder AZ Writer is using. I use the same unit. My longest first shot kill, to date, was 1402 yards on a marmot.

You can do the same with your Kestrel and a good ballistic app like Shooter, but you'll be messing with data every time you shoot long... and don't forget to measure incline.

A great site for long range hunters is longrangehunting.com. Tons of information.

Does gseven.com publish their "tested" BCs for various bullets?