gunsim logo

GunSim Ballistics Software Instructions

Traditionally mobile apps don't need instructions, but this one does.

Q: How do I get the app onto my phone?

A: The easiest way is OTA (Over The Air), you go into your browser and click on the link, or type it in. You click on a couple of confirmation boxes and run the program. To get the Ammo and Bullet databases, you select "Ammo" and then "Bullet" on the app menu.

Q: How do I get the app onto my phone if the phone doesn't have Internet?

A: Email me, I'll send you the files, you'll have to use a USB cable or a Sim chip to transfer.

Q: What is this 1/4 Click thing?

A: Most scopes measure angle in 1/4 minute of angle (MOA) clicks.  In Options you can change this to full minute of angle or mil. The Advanced menu has a multiplier number so you can have 1/8 clicks or whatever you want.

Q: How do I use this to shoot things?:

A: You have to get the Big 6: BC, Muzzle Velocity, Sight Height, Zero, Pressure and Temperature.
BC is probably on the Ammo box, or look it up on the manufacturer's website.
Muzzle velocity you measure with a chronometer. Or look it on the Ammo box, or look it up on the manufacturer's website, that will be for a generic barrel length.
Sight height, distance from muzzle center to front sight tip or Scope front center.
Zero, whatever distance you zeroed at.
Pressure and temperature from a weather website for your area. This will vary.
So type in the above values, type in the range to the target, and you will see the drop in inches and the number of clicks (1/4 Moa) to adjust the vertical elevation turret for the drop. Most people aim off for windage, or you can use the number of clicks on the windage section.
If the drop is 6" and 15 clicks, you aim 6" high, or turn the elevation turret in the direction of the scope's "up" arrow 15 clicks. It is good to mark the elevation and windage turret positions when you zero the rifle. If the calculator says go up 30 clicks for a different range, that is 30 clicks fro your zero setting.

Q: I can't read the numbers, they are squished into tiny boxes:

A: (BlackBerry) Go to the Options screen, the menu has a "Bigger Boxes" feature. The newer BlackBerries have taller screens, and sometime the program doesn't notice, sorry about that. Once the boxes are set to a size you like, the program remembers your preferences.

A: (Nokia) email with what kind of phone you have, this hasn't happened yet.

Q: I zero on the cold mountain, and shoot in the warm valley:

A: The drill is, on the "Data Screen": "Atmosphere changes zero"= No. This is the normal setting, the drop is always 0.0" at the zero range
Enter your original range zero data.
"Atmosphere changes zero"= Yes.
Enter today's atmosphere data.
If you look at the table the drop at your zero might be 0.1" instead of 0.0". It might even still be 0.0" if it wasn't a big change. It will be more noticeable at longer ranges.
Of course, temperature will affect your powder too, and your rifle/scope may expand or contract, the program doesn't model that.

Q: When do I input Altitude?

A: If you know your actual air pressure, you can set Altitude to zero. If you have the weather map pressure (which is the sea level value), you enter altitude and the program adjusts to the height you are actually at.

Q: When do I input Density Altitude?

A: If you know your Density Altitude (from a meter, such as a Kestrel), you don't have to type in pressure, temperature or humidity. Ballistics programs use pressure, temperature and humidity simply to calculate the air density.

The Main Screen:

Ballistics Blackberry

Range is range to the target. The output numbers change as you type.

Uphill angle is in degrees, positive for uphill, negative for downhill. Although the negative sign makes very little difference.

Wind speed is obvious. Wind angle uses a clock code. 3 O'clock is from the right.

Known distance. If your target is 10 inches, you get what that means in angle units (Mil, Moa, 1/4 Moa) at that range. This might be useful for adjusting your point of aim, or verifying the range.

"Drop in" u677.4 means you have to adjust up 677.4 inches. "Drop 1/4 Moa" u256 means turn the elevation knob 259 1/4 Moa clicks in the direction of the "Up" arrow.
Lead is in inches/cm, I assume you will be holding off. Energy, velocity and time, out of interest. Not shown when the rangefinder is on, there wasn't room.



Mil Dot Rangefinding calculator

You can measure range using a mil dot reticle, a known distance, and hard math. Select Options / RangeFinder On. You type in the size of the known object, the number of mil or moa it covers, and the range gets calculated from these 2 numbers automatically, so you just read off the drop.

So, here we have a 1 yard target covering 1 Mil, so the range is 1000 yards, by definition of a Mil. Now, you may have to set the scope to a particular magnification for Mil Dot calculator off in Options, since you may not need it. With the rangefinder off, you get energy, velocity and flight time displayed, and a "Known Distance to MOA/Mil" display instead.

The Data Screen:

The Big Six important things for Drop and Windage are: BC, Muzzle Velocity, Sight Height, Zero, Pressure and Temperature.

If your Pressure is from the weather map (sea level pressure), enter your Altitude. The program adjusts the sea level value to your actual height. If you know the exact Pressure you can set Altitude to zero for no adjustment. If you can measure Density Altitude, then type that in and ignore Pressure, Temperature and Humidity. Otherwise, Density Altitude is zero.

Bullet weight has no effect on Drop and Windage. Humidity has a tiny effect.

Target speed is for lead.

Options Screen:

There are 2 drag models in common use, mostly G1, with G7 for pointy boatails from Barnes. Use G1 if you aren't sure.

Yards / Meters is for range distances only.

Clicks: You have Moa, Mil, or 1/4 Moa to measure angle. Most scopes have 1/4 Moa clicks. You can have a custom angle format using Advanced / "Moa Mil Adjust".

Metric: Metric Atmospherics, inch/cm, speed, energy. Yards / Meters are separate so you can be an American on a Metric range, for example.

You can turn the rangefinder on or off. You probably want it off.

Advanced Screen:

Moa/Mil Adjust: Usually set to 1. If you set it to 0.1, your Mils become tenth of a mil, Moa tenth of Moa. If you set it to 0.125, your Moa becomes 1/8 Moa. If you set it to 0.955108, your Moa become Inch per Hundred Yards. Your scope clicks may be a bit wrong, so you can compensate here.

Coriolis Effect: If the target is far away, the rotation of the earth matters. You need to know your latitude (Southern Hemisphere is negative), and the compass bearing of your muzzle. It is only important at longer ranges.

Spin Drift: Gyroscopic effect move your bullets left (usually). Bryan Litz's formula, based on Bullet diameter, length and barrel twist rate. An approximation, it is only important at longer ranges.

Chrono Distance: For chronograph users, the distance from the chrono to the muzzle. Usually 10 feet.

Bullet and Ammo Database

We have a Bullet and (loaded) Ammmo Database, the same as in the Online Simulator.

First you pick the Manufacturer, then the caliber, then the specific bullet.

There are 3 screens, Manufacturer, Caliber and Bullet weight, you use the back key to go forward as you select. The BlackBerry doesn't have a forward key, sorry. You can use the menu if you prefer.

So you have a Hornady Hunting bullet, select the little circle beside "Hornady - Hunting" and press back.

It is a .308 bullet, so select the little circle beside "0.308" and press back.

It is a RN 110 grain so select the little circle. If you now hit back, the program will use the bullet data in question. Speer bullet data has multiple BC values, these get loaded too.

Ammo is the same, although Ammo changes your muzzle velocity to some kind of typical value.

User Database

You get to save what you type in. And delete individual entries. The information will be there when you exit and restart the program.

Multiple BC's

From the Advanced screen "Mul BC" menu. The G1 BC is accurate for a typical velocity range. At longer ranges, inaccuracy creeps in as the velocity drops. Sierra give you different BC values for different velocities. So type them in (the Bullet database has multiple BC values where available), you can save it in the User Database.

At the bottom of the screen, it lists the data in the same format as the Sierra website to confirm you typed it all in right. There are 14 different numbers to type in in this example, so it is easy to get confused.

For pointy boattail bullets you can use the G7 BC option instead, Berger lists G7 values for most of its bullets. G7 does not have multiple BC values.

We also have a table. The numbers are the Same as the GunSim programs, so you can print the same table online, at have the same information on a luggage tag on your rifle sling. A lo-tech backup is always good. It has wind and drop, velocity, lead and energy. The table scrolls sideways to show all the columns.