KAC Bulletflight app

[BigBear]

So a buddy of mine gifted me with the KAC Bulletflight app for my iphone (Which in itself was a Christmas/Birthday present, lol). I have a few questions on how to fill out certain fields so I may begin using the app...

Sight height
- From top of mount to the middle of the optical lens?

BC1 through BC5 ("ICAO" is under the BC1 slot)
- Don't even know what that means..

Drg
- Don't know what it stands for

Pressure
- Pressue of what? the round leaving the barrel?

%RH
- Don't know what it means.


Thanks for any help.

[68Charger]

I don't know anything about the app, but found this quick:
http://www.knightarmco.com/bulletfli...ght/manual.pdf



Sight height
- barrel centerline to sight centerline (or scope centerline)
the bullet will be this far below the sight line as it leaves the barrel

BC1 through BC5 ("ICAO" is under the BC1 slot)
For BC (ballistic coefficient), the ICAO G1 drag-function is the most common and what nearly all makers use (get this from bullet manufacturer)

Drg
The app accepts G1, G7, or G8 ballistic coefficients You may specify them, for example, by entering G1 or G7 (or simply 1 or 7) into
the Drg field. G7 is best for long-range boat-tail bullets provided you have the correct G7 value to use.

Pressure
- Barometric pressure

%RH
- Relative Humidity

[BigBear]

Thank you Sir.

Do you happen to know what G1-7 specifically notates?

[68Charger]

Thank you Sir.

Do you happen to know what G1-7 specifically notates?

It's based on different "models" for bullet profiles... from Wikipedia (I know, I know)...
http://en.wikipedia.org/wiki/Ballistic_coefficient
Differing mathematical models and bullet ballistic coefficients

Most ballistic mathematical models and hence tables or software takes for granted that one specific drag function correctly describes the drag and hence the flight characteristics of a bullet related to its ballistics coefficient. Those models do not differentiate between wadcutter, flat-based, spitzer, boat-tail, very-low-drag, etc. bullet types or shapes. They assume one invariable drag function as indicated by the published BC. Several different drag curve models optimized for several standard projectile shapes are however available.
The resulting drag curve models for several standard projectile shapes or types are referred to as the:

• G1 or Ingalls (by far the most popular)
• G2 (Aberdeen J projectile)
• G5 (short 7.5° boat-tail, 6.19 calibers long tangent ogive)
• G6 (flatbase, 6 calibers long secant ogive)
• G7 (long 7.5° boat-tail, 10 calibers tangent ogive, preferred by some manufacturers for very-low-drag bullets[10])
• G8 (flatbase, 10 calibers long secant ogive)
• GL (blunt lead nose)

More info, better detail, and some history:
http://www.exteriorballistics.com/eb...oefficient.pdf

look at the bottom of page 6 for G1 vs G7 description

also found this in my bookmarks, lots of info here, too:
http://www.frfrogspad.com/extbal.htm

[BigBear]

Very interesting... so, then I need to figure out what my bullet actually is then. I'm assuming the manufacturer's website would have that info.

Thanks for the help, it's much appreciated.

[BigBear]

More questions:

For the windage, pressure, etc I would need to obtain a "Kestrel" correct?
- Working on becoming competent on calling wind and stuff but I need help currently.

What does "Pressure InHG" mean?
- This seems to be a different field that the barometric pressure.

What does the "-" click mean?
- I'm assuming positive numbers mean I turn turret to the right, and negative numbers to the left? (i.e. positive up, negs down)??

And before I get around to using this, I should really figure out what type of ammo the gun likes best anyways right?

[Tim K]

You need to be able to measure wind speed, barometric pressure, temperature, and humidity. Actually, humidity has a limited effect so it's not so critical. The Kestrel 4500 measures all the variables in one unit. It's expensive, but convenient. Less expensive models have fewer features, but you may have the ability to make some measurements already. If you own a handheld gps, it might have a barometer, or maybe you own an altimeter watch. Temperature is easy, and as stated before humidity is not critical.

If you don't have a barometer of some sort already, then the 4500 is the answer.

Barometric Pressure is measured in either inches or millimeters of mercury, abbreviated "inHg" or "mmHg".

The click sign (positive or negative) should be intuitive. Don't let the sign confuse you. If you have a 100 yard zero and are getting dope for 400y, you know you have to turn the dial in the "up" direction.

[Tim K]

Forgot to answer your question about figuring out the ammo your rifle prefers.

It's a good idea, but not essential to begin using the app. What is essential is to know the muzzle velocity. Most guys will figure out a load they like, then determine the bullets BC and muzzle velocity. One you get from the bullet manufacturer, the MV you measure.

You can generate dope for any number or loads, you'll just have to chrono them all to get decent data. I currently have dope for three different loads for one rifle. It's a bit of a bookkeeping hassle, but not impossible.

[BigBear]

You need to be able to measure wind speed, barometric pressure, temperature, and humidity..... The Kestrel 4500 measures all the variables in one unit...

Barometric Pressure is measured in either inches or millimeters of mercury, abbreviated "inHg" or "mmHg".

The click sign (positive or negative) should be intuitive. Don't let the sign confuse you. If you have a 100 yard zero and are getting dope for 400y, you know you have to turn the dial in the "up" direction.

Rgr, thanks. The click sign is pretty intuitive but I wanted to make sure that I was just reading the +/- correctly as in plus would equal up for farther range, etc... Thanks.

Forgot to answer your question about figuring out the ammo your rifle prefers.

It's a good idea, but not essential to begin using the app. What is essential is to know the muzzle velocity....

How does the muzzle velocity effect function (beyond the obvious power sublties and flatter trajectory, etc)?

Why would muzzle velocity be more important than knowing what your rifle likes to eat? Doesn't knowing what teh rifle likes to eat help equate into smaller "groups"?

[Tim K]

Muzzle velocity is a critical number for your new app to use to determine your dope. It's not critical that it be high or low, it's only critical that you know what it is. Definitely choose the load that gives best accuracy, then chrono it to find out the MV. Don't care what the number is, just need it for the calculations.