Internal ballistics refers to the science of what occurs inside a firearm from ignition until the projectile exits the barrel. It involves three phases: lock time, ignition time, and barrel time. Factors that influence internal ballistics include propellant type and burn rate, bore size, bullet size, loading density, chamber pressure, and barrel length. Understanding internal ballistics helps maximize a firearm's accuracy, range, rate of fire, and damage potential.

1. INTERNAL BALLISTICS
Ryan Begley

2. What is Internal Ballistics?
◻ Ballistics is the science of launching projectiles
using propellant or gunpowder
◻ Internal Ballistics is the science of what goes on
inside of the gun
1. Lock time, the time from sear release until the
primer is struck
2. Ignition time, the time from when the primer is
struck until the projectile starts to move
3. Barrel time, the time from when the projectile
starts to move until it exits the barrel.

3. History of Ballistics
◻ Ballistics began with the invention of the first
muzzle loading cannons in the 1200’s A.D.
◻ The first handheld guns were muzzle loading
rifles and were developed in the 1400’s
◻ The first guns were smoothbores

4. Beginning of Internal Ballistics
◻ Since the invention of the first firearms, people
have been trying to maximize:
◻ Accuracy
◻ Range
◻ Fire Rate
◻ Damage

5. Parts of a Working Firearm

6. Parts of A Semi-Automatic Pistol
CZ (Česká Zbrojovka) 75B 9mm Pistol

7. Rimfire cartridge on the left Centerfire cartridge on the right
Cartridges

8. Propellants and Burn Rates
◻ Fast burn rates
◻ Inconsistent
◻ unstable
◻ Slower burn rates
◻ Increased velocity
◻ Consistent
◻ Different shapes of
grains for different
surface areas
Black Powder Modern Smokeless Powder

9. Burn Rate Equation
◻ where BR is Burn Rate
◻ β and α are found empirically with experiments
◻ ζ (zeta) is the burn augmentation factor that
accounts for energy from grain fracture and
inconsistent grain burning
◻ υ is the projectile velocity

10. Bore Size
◻ A firearm, in many ways, is
like a piston engine on the
power stroke. There is a
certain amount of high-
pressure gas available, and
energy is extracted from it by
making the gas move a
piston — in this case, the
projectile is the piston

11. Bullet Size
◻ The caliber of the gun is usually the diameter of the bore
◻ Most guns are maximized for length, based on the velocity of the
normal projectile weight
◻ 120 calibers

12. Loading Density
◻ Ratio of the weight of the powder charge to the
capacity of the powder chamber
◻ Measured in grains
◻ More fully the powder charge fills the case the
more consistent and accurate the load will be

13. Chamber Pressure
Pressure is measured
with Strain Gauge

14. Barrel Length
◻ Measured from the face of the muzzle to the base of the
seated bullet
◻ Barrel length determines muzzle velocity
◻ Velocity increases with barrel length up to a certain length
dependent on bullet size and propellant
◻ Typical barrel lengths:
18-24 inches for rifles
2-8 inches for handguns
Velocity Range
Vel change
per inch
0-2000 5-10
2000-2500 10-20
2500-3000 20-30
3000-3500 30-40

15. Rifling

16. What Happens when the Trigger is pulled?
http://www.youtube.com/watch?v=AqMzUsTTFnA

17. Firearm Identification
The Extractor, Extracting Pin, Breechbolt, and Firing Pin all leave
distinguishable marks on the empty cases

18. Types of Marks Left on Cases

19. Resources
1. Allen, CTD. "Interior Ballistics." The Shooters Log. Cheaper
Than Dirt, 24 Aug. 2012. Web. 28 Feb. 2013.
2. "Ballistics." AuthorSTREAM. N.p., n.d. Web. 28 Feb. 2013.
3. "FirearmsID.com- An Introduction to Forensic Firearm
Identification." FirearmsID.com. N.p., n.d. Web. 28 Feb. 2013.
4. "Hornady." Internal Ballistics. Hornady Manufacturing, 2013.
Web. 28 Feb. 2013.
5. Klatt, Edward C. "FIREARMS TUTORIAL." FIREARMS
TUTORIAL. University of Utah, n.d. Web. 28 Feb. 2013.
6. Schaefer, J. C. "A (Very) Short Course in Internal Ballistics."
Internal Ballistics. J. C. Schaefer, 28 July 2012. Web. 28 Feb.
2013.
7. "Internal Ballistics." Wikipedia. Wikimedia Foundation, 20 Apr.
2013. Web. 21 Apr. 2013.