Chapter 29: Ballistics

  • Rifling → the internal grooves of a firearm barrel that impart spin to the projectile, enhancing its stability and accuracy during flight.

    • Described as a twist rate → the distance the bullet must travel to complete one full revolution.

      • A shorter distance indicates a faster twist rate, so the bullet will have a higher spin rate.

  • Swaging → rifling technique involves the use of cold-working to harden the interior of the barrel and permits the use of cheaper mild steel

  • Electrochemical Etching → rifling technique that involves applying a voltage between the barrel and an electrode resulting in the barrel becoming the anode in an electrochemical cell

  • Caliber → the diameter of a circle that is tangent with the top of the lands of the rifling

SOFT LEAD

  • The bullets hold together after impact well and will expand somewhat.

  • Transfer energy well, maintain velocity well, and are used for both high- and low-velocity applications.

  • Very low tech and easy to make, which results in many homemade versions of the soft lead bullet

PARTIAL JACK, SOFT POINT

  • Complex construction: a lead core with copper jacket.

  • Designed to enhance expansion yet maintain weight

  • Larger wound channels, as the energy expands behind the traveling bullet, due to better energy transfer from the bullet to the target.

FULL METAL JACK

  • Rugged bullet type, which can tolerate rough handling

  • Driven at a very high velocity very accurately and results in a limited wound channel due to very little expansion and little transfer of energy.

  • The major damage is done by the shock wave, and this results in more hard tissue damaged.

HALLOW POINT

  • Consists of a metal jacket, but the tip is hollow — allows for more expansion than soft point at lower velocities, which means more energy transfer at lower velocities.

  • Excellent handgun projectile that can cause a large amount of soft tissue damage.

  • High tech to manufacture

SHOT

  • Multiple projectiles that come in a variety of sizes

  • Calculate energy on the basis of individual pellets to determine the amount of damage it will do

  • Results in a jagged wound channel and is primarily a short-range bullet.

  • Most common type of projective for a shotgun

EXPLOSIVE

  • Made by inserting percussion caps into the hollowed‑out noses of hollow‑point bullets

    • A percussion cap contains a shock‑sensitive explosive compound.

    • When placed in the cavity of a hollow‑point bullet, it can detonate on impact, causing fragmentation or an explosive effect.

    • This design is historically documented and is considered an explosive projectile, not a soft‑point or lead‑alloy round.

  • Modern gunpowders are also described as “single base” when the basic ingredient is nitrocellulose and as “double base” when there is additionally 1–40% nitroglycerine added.

  • All gunpowders are designed to burn quickly to produce rapid expansion of gas in a confined space. In an explosion something gets very big very fast. The burning rate of gunpowder can be classified in three categories:

    • Degressive (regressive) burning: gunpowder grains formed in flakes, balls, and sticks have a burning surface area that decreases continuously as the grains are consumed.

    • Neutral burning: gunpowder grains that are single perforated and the burning surface area remains relatively constant.

    • Progressive burning: gunpowder grains that are multiperforated and rosettes that have a burning surface area that increases continuously as the grains are consumed.

  • Sodium Rhodizonate Color Test → reacts with the lead components of gunshot residue and is indicative of a scarlet color

  • Interior Ballistics → regime is which the chemical energy stored in the propellant is converted into the kinetic energy of the projectile

  • A hook cutter makes one grooves in one swipe

  • A scrape cutter makes two grooves in one swipe

  • Projectile →any material that travels through space by the exertion of a force.

  • The slide or breechblock of a semiautomatic pistol is moved back by the energy produced by the fired cartridge.

  • Primer cap is the part of the cartridge that will firing pins mark

  • The helixometer is the he specialized tool used to measure the number, direction, and degree of twist of rifling lands and grooves inside a firearm barrel.

  • Chemical Etching → the method that takes advantage of the compressed, weakened metal structure beneath a stamped serial number to recover obliterated markings.