Caliber and Ammunition - Hand Guns and Rifles

Modern rifle and hand gun ammunition consists of primarily four parts: a primer (or cap); a case (or shell); gun powder; and a bullet. Here's a look at a center fire rifle and a hand gun cartridge borrowed from .

Bullet – a single projectile fired from a firearm. Some mistakenly consider the entire round of ammunition to be the bullet, in actuality it is only the tip of the round.

Case – usually made of brass and contains the powder charge, the primer and the bullet. Before development of the metallic cartridge, the term was used to mean a roll or case of paper containing powder and shot. A center fire cartridge refers all pistol and rifle cartridges that have primers in the center of the base, while rim fire cartridges have primer in the rim.

Crimp – the portion of a cartridge case that is bent inward to hold the bullet in place.

Powder – the general term for any chemical compound or mixture used in firearms that burns upon ignition. The gases produced by this rapid combustion propel the bullet down the bore. One major type is black powder, which is a mixture of charcoal, sulfur and saltpeter. It’s used in older cartridges. Another major type is smokeless powder, which is principally used in modern ammunition. It’s a granular nitrated chemical compound.

Primer – the collective term for the chemical primer compound, cup and anvil. When the primer is struck, it ignites the powder charge.

Rim – the edge on the base of a cartridge case. It’s the part of the case gripped by the extractor to remove it from the chamber. In some cartridges it also prevents the case from entering the chamber.

The additional numbers and descriptions for ammunition cartridges indicate changes in the casing,bullet design, amount of powder, etc. to change various aspects of performance such as recoil, velocity, trajectory, accuracy and what happens to the bullet when it meets its target. Modern bullets may also incorporate aerodynamic designs for accuracy over ranges of several hundreds yards. Bullets can also be made from various combinations of materials (lead, copper etc.), equipped with tips designed to pierce various materials or to explode on impact. Modern ballistics (cartridge and bullet design) is a full fledged science - click on the book cover to see an example table of contents. We'll just provide a few examples.

Some cartridges with reduced recoil are intended for "tactical" (personal protection) use and some are "cowboy" loads which are designed for demonstration or gun shows. Changes in recoil are typically accomplished with the quality or quantity of the gunpowder or primer.

Another example is the .30-06 (pronounced “thirty-aught-six”, "thirty-oh-six"). The .30-06 is a .30 caliber cartridge was originally developed for the military in 1906 to meet a need for improved long range machine gun performance. The powder load (increased for power and range) and bullet shape (more aerodynamic) vastly improved velocity, range, accuracy and caused devastating damage when equipped with deforming or fragmenting bullets. The .30-06 was the U.S. military round for 50 years and remains widely used today. Check out this article in Wikipedia for more details.

When bullets strike a target, they can cause damage by striking vital body parts, causing bleeding, and by the transfer of energy (shock). Larger caliber bullets generally cause more damage than smaller caliber bullets and higher velocity bullets generally cause more damage than slower moving bullets. Damage is also caused by bullets that deform (change shape) or fragment upon impact. A fragmenting bullet acts like shrapnel causing multiple paths of damage from a single shot.

A deforming bullet looses its aerodynamic shape and increases the diameter and surface area on the front of the bullet once it enters its target. Rather than passing cleanly through the target, the kinetic energy of the bullet in motion is quickly transferred to the target by a pressure wave created from inside the target. This pressure wave causes damage, hydrostatic shock , to a much larger area than simply the path of the bullet moving through the target.

The illustrations at right are still photos from a high speed video of the deforming bullet passing through a 3-inch section of ballistics gel. Note how quickly the bullet deforms and the pressure wave begins. The final illustration shows how the shock wave fully engulfs the ballistic jell causing wide spread damage.

Click on the pictures at right to see the video, or a video of the Barnes Bullets fragmenting round called the Varmint Grenade. Caution , this video shows real kills and can be a shock if you're not prepared.