Advanced Marksmanship Problem with KAC Bullet Flight App

[The Zebra]

Need some help here. I have the Bullet Flight app on my iphone ($20 version). Everytime I enter the range into the calculator, I do not get an accurate dope to dial in. This is for any rifle that I attempt to use the app with. Example:

R700 in .308. 175 SMK @ 2605 fps. BC taken from Sierra's site (G1 0.495). 200 yard zero and local weather info weather utilized. Angle set to zero.

Real world dopes with this this rifle:
200 yard zero
8.25 MOA @ 400 yards
16 MOA @ 600 yards
21.25 MOA @ 700
26.75 MOA @ 800

App is giving me these numbers:
200 yard zero
6 MOA @ 400
13.8 MOA @ 600
18.5 MOA @ 700
23.8 MOA @ 800

I have tried adjusting the velocity in the app to meet the real numbers but when I get the 400 yard dope matched, all other numbers are out of wack, and so on.

Does anybody have any insight of what I am doing wrong or what I can do differently to make this work? I feel like this has been a waste of $20. Like I mentioned before, the numbers are off with any rifle/ammo combo that I throw into it. I am getting all of my BC numbers from the manufacturer's websites.

 

[Lowlight]

Re: Problem with KAC Bullet Flight App

You're real world closer matches a rifle with a 100 yard zero... not a 200 yard zero.

 

[CoryT]

Re: Problem with KAC Bullet Flight App

The real world numbers given don't seem to track for me. Have you calibrated the scope? How precise are the ranges? What is the group size at each range, and how many shots are you using for a group? What is the target/aiming point? What is the load, because that seems pretty slow?

The app numbers you show track quite well to my personal rifles and that of a number of student guns. Nominal up for a 175 308 from a 100 yard zero to 600 is 15-16 MOA. with 1.5 - 2 MOA being pretty common for 100-200, that puts the 13.8 you show right in there.

Given that you have multiple rifles with the same symptoms, I suspect some kind of error in the actual ranges / zero values, since the app tracks to mine (FFS) and the app data seems to line up well with many rifles I've seen here for classes. Is it possible you really have the rifle at 100 for the actual zero? If you need 8.25 MOA up to get to 400 with a .308 zeroed at 200, there's a whole lot more wrong than the app.

 

[CoryT]

Re: Problem with KAC Bullet Flight App

Good morning LL.

 

[Lowlight]

Re: Problem with KAC Bullet Flight App

Howdy Cory,

 

[The Zebra]

Re: Problem with KAC Bullet Flight App

CoryT,
Thanks for the input. I feel a bit stupid to admit that I'm not sure what you mean by "calibrate the scope" so I guess no I haven't done it. Ranges are lased with a Bushnell Fusion 1600. Group size at each range is different but all are under 2 MOA (that would be the shooter's fault, not the gun). Elevation is on for the 5 shot groups but my windage left something to be desired. Target is a USPSA shaped steel ringer with a (I think 12")flapper at center mass. Flapper sprayed orange and that was my aiming point. Target located about 5 feet off of the ground. Load is 44.7 gr. of Varget, CCI BR-2 primer, Lapua brass trimmed to 2.005" and 175 SMK seated to 2.855" COAL.

I am 100% sure on the zero distance. I was zeroing it for the first time with my new NF. Zeroed at 200 and got dopes out to 800 in the same session.

As previously mentioned, the app gave the same problem with my Savage FV-SR 22. Dopes were off for actual shooting distances.

 

[CoryT]

Re: Problem with KAC Bullet Flight App

Calibrating the scope is required so we know what you actually have dialed on, as opposed to what the knobs indicate. Many ways of getting that done, do a quick search and you'll find several threads with various methods.

Is it possible the LRF is set to meters? 44+ of Varget should deliver 2600-2700 depending on the barrel/chamber, so the velocity seems reasonable.

Given the fairly large aiming point and group size, I'd have a hard time saying the 'actual' numbers were in fact correct.

What are you using for weather? For example, if you are getting a baro reading from the local weather station and using that as station pressure, that would be one source of error. If your Kestrel is not set correctly you'll have a similar issue.

 

[Enough Said]

Re: Problem with KAC Bullet Flight App

BulletFlight is not the problem, 'Zebra. Not solely at fault, anyway. Keep the program and work with it until you have the relationship between the ammo, scope, rifle, weather and data worked out to cold-bore hits!

 

[pshell]

Re: Problem with KAC Bullet Flight App

OP,
I had/have the same problem with the KAC software. I can get it to match up with the back or front end of the ballistic curve, but not the whole thing. I eventually just went back to collecting information in a given environment. The software just didn't work for me. I would much rather plan ahead of time so I can collet elevation data rather than depend on a computer to guess for me. Keep dicking around with that stuff and you have quickly shot enough rounds to have zeroed and confirmed out to 1000m, in 100m intervals. Conceptually it's pretty cool, but in practice that stuff leaves much to be desired.
I think people see ballistic software as an aid to new(er) shooters, giving them the edge so to speak. In reality, I see new guys use ballistic software instead of learning to read the wind and collect elevation data. It seems to result in a loss of comprehension and trust in the hardware. Guys like to think the software is right and the gun is wrong, which has been the opposite of my experience. The software will get you close but it has been less than reliable on the backside, for me. At distance it will put you off target unless you true it, which you can't do with the KAC stuff. If your truing it, why not just shoot the front side and the backside of the curve? Food for thought. If you figure it out, let us know.