What is NOBal Comp? - NOBal Comp stands for Nerdulator.net Online Ballistics Computer. It is a simpler, online implimentation of it's big brother, GNU Exterior Ballistics Computer created by Derek Yates and updated specifically for the iPhone and iPod Touch by Mat Pridham. Simply put, a ballistics computer is a projectile calculator... If you're into shooting and have not yet used a ballistics calculator, you owe it to yourself to give it a try.
Ballistic coefficient - The coefficient of drag for your bullet, using a G1 drag function. This can be found in your bullet manufacturer's documentation. All published BC's are for the G1 drag function unless they explicitly state otherwise, and are generally a number between 0.300 - 1.000.
Projectile Weight - The weight of your bullet, in grains. This can usually be found on the bullet box or in the manufacturer's published data.
Initial Velocity - The muzzle velocity of your bullet / rifle combination. The best way to get this is with a chronograph, but you can also estimate it from known combinations. For example, a 168gr SMK generally shoots about 2650 ft/s out of a 26" barrel in most match grade loads. This is acceptable, but for the best accuracy consider borrowing or buying a chronograph.
Zero Range - The range at which your rifle is set to "zero". If you zero your rifle on a 50 yard range, this would be 50 yards. A popular zero for many hunting rifles is 200 yards, which seems to be a good compromise between bullet path and maximum point blank range.
Sight Height - The height of the sighting system of your rifle above the bore of the rifle. For scopes this is usually between 1.5-1.8, but the bigger your scope and the taller your scope rings, the larger this will be. An easy way to measure is to measure from the bottom of your scope objective bell to the top of your rifle barrel, then add this number + the objective bell's radius + the barrel's radius (at the point you measured), to get a very close approximation.
Angle to Target - If you are shooting up-hill or down-hill at your target there can be a big change in the bullet trajectory. For up-hill angles use positive angles and for down-hill use negative. Example: If your favorite hunting location is from the top of a hill looking into a valley, you might shoot at a down-hill angle of 30 degrees. For this scenario you should use the value -30 here to generate an accurate ballistics table.
Wind Velocity - The wind speed in miles per hour. There are several good ways of estimating wind speed, but the best is to measure it with an anemometer.
Wind Angle - If you wish to generate a windage table you need to enter the angle from which the wind is blowing. In this simulator, a direct headwind is 0 degrees, a wind from right to left is 90 degrees, a tail wind is 180 degrees, and a wind from left to right is 270 degrees (or -90 degrees).
Max Range - The maximum range you need data for. The engine will give up whenever the bullet is dropping faster than it is progressing forwards, so you can't get data at extreme long ranges for most cartridges. But this will cover all possible shots that you might actually be able to make, for any cartridge up to small artillery.
Step Size - My hosting company gets a little upset when this script uses up all the resources, since ballistics calculations can be quite intensive. To speed things up a bit I have added this step size. The solution is just as accurate, but the solution won't store data for every yard. If you enter a step size of 10, you will get data for every 10 yards, which uses up only 1/10th the memory of a standard solution with no loss of accuracy.
Other Questions? - For ballistic engine related questions you can email Derek: derek@nerdulator.net. He wrote the ballistics library, and the offline GNU Exterior Ballistics Computer, so he can probably answer whatever questions you have.
- For NOBal Comp specific questions (i.e. questions about the iPhone specific version) please contact us here at WebDiligence.ca
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