HappyHellfire
Silver $$ Contributor
Hi, I'm Dr. John Stutz and I teach ballistics to engineers and scientist. Did you know that there are multiple different ways to calculate bullet drop?
The first way is called the vacuum method. Many people learned this in high school physics. This method is still useful for long range rifle fire and is still taught. For example, the Rifleman's Rule to adjust for shooting up or down hill is derived from the simple vacuum model. It is also pretty good for a quick estimate for things like pistols and short distance rifle.
The second set of methods is called the flat fire models. We can assume the drag coefficient is constant for subsonic or extreme hypersonic bullets. We can also assume a k/M or k/sqrt(M) for the drag coefficient and the math becomes directly solvable (with assumptions of course). Finally we can create integration tables for the drag curve (Ingalls or Siacci Tables) and use the Siacci Method to solve for drop which is what is taught as a backup method in sniper schools.
We can also write a ballistic stimulation of the bullet to measure the drop. These also come in several different flavors. The simplest is a 2 degree of freedom (2DOF) that only measures range and drop. We have developed much more complex simulations like the 4DOF NATO standard simulation which is based upon the work of Lieske at BRL in the 80s. Finally we have full 6DOF ballistic models which model all of the forces on a bullet and are very accurate but run very slowly.
Finally, we have the good old empirical or testing model. Take the sucker to the range and shoot at different ranges to find drop and interpolate between them.
Each method has it's strengths and weaknesses.
What method do you use? If you use a ballistic calculator, what method is it using? Knowing the method your calculator uses will help you know the approximations that it is making.
The first way is called the vacuum method. Many people learned this in high school physics. This method is still useful for long range rifle fire and is still taught. For example, the Rifleman's Rule to adjust for shooting up or down hill is derived from the simple vacuum model. It is also pretty good for a quick estimate for things like pistols and short distance rifle.
The second set of methods is called the flat fire models. We can assume the drag coefficient is constant for subsonic or extreme hypersonic bullets. We can also assume a k/M or k/sqrt(M) for the drag coefficient and the math becomes directly solvable (with assumptions of course). Finally we can create integration tables for the drag curve (Ingalls or Siacci Tables) and use the Siacci Method to solve for drop which is what is taught as a backup method in sniper schools.
We can also write a ballistic stimulation of the bullet to measure the drop. These also come in several different flavors. The simplest is a 2 degree of freedom (2DOF) that only measures range and drop. We have developed much more complex simulations like the 4DOF NATO standard simulation which is based upon the work of Lieske at BRL in the 80s. Finally we have full 6DOF ballistic models which model all of the forces on a bullet and are very accurate but run very slowly.
Finally, we have the good old empirical or testing model. Take the sucker to the range and shoot at different ranges to find drop and interpolate between them.
Each method has it's strengths and weaknesses.
What method do you use? If you use a ballistic calculator, what method is it using? Knowing the method your calculator uses will help you know the approximations that it is making.
