Branches of Ballistics

Interior Ballistics

This branch of ballistics studies the motion of projectiles while they are still inside the firearm.

Bullets, and other ammunition, are affected by interior ballistics over a very short period. In a modern rifle, it only takes about 0.01 seconds from when the firing pin is hit to when the bullet leaves the muzzle.

These are the events that happen inside the firearm when the trigger is pulled:

1. firing pin hits the primer
2. primer ignites
3. flames are produced
4. gunpowder combusts
5. heated gas expands
6. pressure develops
7. energy is generated
8. bullet fires
9. recoil occurs
   
   Recoil is defined as the equal and opposite reaction of the gun against the forward movement of the bullet. Jump is a related term that names a part of recoil. Specifically, the jump is characterized as the backward and upward movement of the gun that takes place before the bullet leaves the muzzle.

Interior ballistics studies each of these steps of the movement of the bullet along with its velocity and rotation. Additionally, engravings on the cylindrical surface of bullets are also studied

Special Notes

Benjamin Robins, mentioned in the previous lesson, conducted many experiments in interior ballistics. His findings earned him the tile of “father of modern gunnery.”

Benjamin Thompson made the first attempt to measure the pressure generated by gunpowder late in the 18th century.

Exterior Ballistics

This branch of ballistics studies the motion of projectiles from the moment they leave firearms to the moment before impact. Most bullets today do not fly for more than 30 seconds at maximum range.

Related Terms

• muzzle blast the noise created at the muzzle point of a gun
• muzzle energy this refers to the energy generated at the muzzle point
• trajectory path taken by a projectile in flight
• range imaginary straight distance between the muzzle of a gun and the target
  • accurate range the distance within which the shooter or gunner has control of his shots
  • effective range the distance within which a fired bullet is capable of inflicting fatal injury
  • maximum range the furthest distance a bullet can travel
• velocity speed and direction of the bullet

Terminal Ballistics

This branch of ballistics studies the effects of projectiles on the target. Of prime interest to sportsmen and the military is the penetration of the projectile as it helps in determining safety requirements.

Important Terms

• terminal accuracy size of the bullet grouping on the target
• terminal energy / striking energy the force of the projectile when it strikes the target
• terminal velocity the speed of the projectile upon hitting the target
• terminal penetration depth of entry of the bullet upon striking the target

Forensic Ballistics

This refers to the application of ballistics to the law. The word “forensic” is derived from the Latin word “forum” which refers to a marketplace where people gather to discourse. When used with a field of science, such as ballistics, it suggests a relationship to the courts of justice or legal proceedings.

Scope

• Field Investigation
• Technical Examination of Exhibits
• Legal Proceedings