Introduction
The goals of this topic will be to...
- Define the most commonly found types of bullets and casings
- Discuss the purposes and functions of each type
- Clarify common misconceptions related to ammunition
Elements of Ammunition
Essential Components
The earliest firearms consisted of nothing more than a barrel with the open muzzle at the front and a closed chamber at the rear, with a small hole - the flash hole - in the chamber to facilitate the ignition of the powder charge within from the exterior of the firearm. To fire these early guns, the user needed...
- Powder - in this case black powder, referred to then simply as gunpowder - a volatile mixture of charcoal, sulfur, and saltpetre (potassium nitrate) which when exposed to flame would ignite, expelling huge volumes of expanding gas, suitable for propelling a projectile when funneled by the confines of a barrel.
- Bullet - A projectile which fit in the barrel and was rammed back to the chamber in front of the waiting powder, and which would be expelled upon the powder's ignition. Early bullets were typically stone or other crude materials, though as time went on these evolved into lead balls, whose density made them better suited for ballistic flight by increasing momentum and resisting the effects of the wind.
- (Optionally) Primer - A smaller, secondary powder charge, which protruded through the flash hole and could be lit from outside the barrel, burning and igniting the main charge. Some early firearms, especially artillery pieces, did not feature this secondary priming powder charge, a lit match or cord was simply pushed through the flash hole to ignite the main charge.
Evolution of Ammunition
As time progressed and firearms evolved, it became apparent that their greatest weakness was the sluggishness with which they could be reloaded - even the most well-trained and equipped riflemen could not fire more than three to four shots during one minute of battle.
A number of developments contributed to speeding up this process, including the breech-loading firearm, whose barrel opened at the rear to facilitate loading, and whose operation was aided by the cartridge, a paper sleeve containing a pre-determined amount of powder and often the bullet, which was used for loading traditional muzzle-loading firearms as well, but had its effectiveness multiplied by the breech-loader's ability to have the cartridge inserted at the rear of the barrel where the operator was better able to manipulate the gun. This firing was also sped along by the introduction of the percussion cap, a small brass fixture containing a percussion-sensitive explosive that, when crushed by a firearm's hammer, would produce a flame, funneled into the chamber to ignite the powder charge. These percussion caps served as the firearm's primer, and eventually led to the development of the explosive pellets now simply called primers.
At this point in history - around 1850 - the Sharps rifle embodied the most modern firearms technology: It loaded a cartridge with bullet and powder inside from the breech, and had a nipple over which percussion caps were placed to be struck by the rifle's hammer to ignite the charge.
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| The Sharps Rifle Image Source: Wikimedia Commons |
The Self-Contained Metallic Cartridge
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| Various types and calibers of ammunition |
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| Cartridges for scale |
The self-contained metallic cartridge is comprised of four elements: Bullet, powder, primer, and characteristically - a metallic casing which holds all of these elements together as a single unit. This unit is most commonly simply called a cartridge, but is also a round of ammunition. Bullet is also commonly used, though technically incorrect if referencing the entire cartridge.
These cartridges can be separated by numerous characteristics, including the shape of the case, how the primer is installed, the shape of the bullet, and countless other metrics. The particulars of each cartridge (manufacturer, bullet weight, product line) will not be delved into for the purposes of this feature, we will instead be using each of these numbered cartridges to identify visually the characteristics we will be discussing.
Components of a Cartridge
Handgun and Rifle Cartridges
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| A. Bullet B. Metallic Case C. Primer D. Powder |
Shotgun Cartridges
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| A. Shot B. Shell C. Primer D. Powder E. Shot Cup |
Shotgun cartridges (typically shotgun shells, shotshells, or simply shells) differ in a number of ways from handgun and rifle cartridges. Most noticeably, the body of the casing (or shell, hull) is mostly plastic, with a metallic base. Housed in this metallic base is the powder charge, while the projectiles (the shot - lead balls) in the case of this cartridge, are contained in a plastic shot cup in the above plastic section. This shot cup acts to hold the pellets of shot together as they are propelled from the barrel, preventing them from expanding into wide patterns until they have reached a certain distance.
Rimfire Cartridges
Rimfire cartridges are unique in that they contain their primer integrally within the metallic case. The pronounced rim visible at the base of the casing contains a priming compound, and when the base is crushed, this compound detonates, igniting the main powder charge. While lacking in power compared to typical centerfire cartridges, rimfire cartridges have been around for over a century, and have withstood the test of time due to their ease and affordability of manufacturing.
Bullets / Projectiles
Bullets feature differing shapes, compositions, and weights designed to achieve the goals of a particular cartridge, or serve a particular function. Some of the most common bullet "styles" include...
- Full Metal Jacket (or FMJ) - A metallic shell or jacket, most frequently made of copper, surrounds a lead projectile, making the bullet sturdier, less likely to deform upon striking a target, and capable of being propelled more quickly through rifled barrels without being damaged. These bullets are extremely common, as they are affordable both to buy and to manufacture.
Cartridges featuring FMJ bullets: 3, 4, 5, and 10 - Hollow Point (or HP) - A bullet which has a hollow cavity at the front, designed to be pushed apart and expand upon striking a target. These bullets come in several varieties, such as the jacketed hollow point (JHP) - a hollow point bullet with a metal jacket, seen on cartridges 1 and 8; The semi-jacketed hollow point (SJHP) - a hollow point bullet with a partial metal jacket, seen on cartridge 6; as well as certain proprietary configurations, such as the "FTX" bullet in cartridge 2, a jacketed hollow point bullet with a polymer insert designed to prevent the cavity from becoming clogged, which would hinder expansion.
Cartridges featuring HP bullets: 1, 2, 6, and 8 - Lead Round Nose (or LRN) - A bullet made of solid lead without a metallic jacket, with a rounded front point, commonly used for affordable practice and target ammunition.
Cartridges featuring LRN bullets: 9 - Wadcutter (or WC) - A lead bullet with a flat front designed to punch clean circular holes through paper for the purpose of competition shooting. Semi-Wadcutters also exist, and are distinct from wadcutters in that they combine the traditional rounded shape with the wadcutter's flat tip to serve as an all-around, multi-purpose bullet.
Cartridge 7 features a Semi-Wadcutter bullet.
The two shotgun shells pictured (11 and 12) utilize shot, a multitude of lead or steel balls (occasionally plated with another metal) of different sizes depending on the shell's intended use, which are typically used in a shotgun's smoothbore (or without rifling) barrel to achieve a certain spread or pattern as the balls travel away from the muzzle. Shell 11 uses birdshot, pictured above in the Components of a Cartridge section, designed to spread into broad patterns at range for hunting birds. Shell 12 by contrast uses buckshot, much larger and more massive spheres for hunting larger game.
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| Birdshot on the left, Buckshot on the right. Notice the much larger brass base on the buckshot shell, needed to contain the extra powder used to propel the larger shot. |
Case Composition
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| Different metallic cases of 9x19mm handgun cartridges |
The metallic cartridge case serves several purposes. It first and foremost contains all the necessary components for firing a gun in a single, easily manipulated unit. It also serves to seal the barrel when the gun is discharged, as the heat of burning gunpowder will cause the case to expand to fit the walls of the chamber. Lastly, this heat absorbed by the casing can be extracted and ejected from the gun with the casing, rather than being absorbed by the gun itself, which would increase wear on the firearm's components.
The composition of cases varies, but they are most commonly made of brass (cartridge 3 above), followed by steel (cartridge 5 above). Brass offers a good balance between cost of manufacturing, flexibility for the purpose of expansion, heat absorption, and durability for reloading spent cases. Steel is used for low-cost manufacturing, and is often seen in military surplus ammunition from former Warsaw Pact countries - it offers inferior expansion, heat absorption, and durability compared to brass, and typically cannot be reloaded after firing.
Other materials are less common, but serve their own purposes. Nickel-plated brass, as seen on cartridges 1 and 2 above, does not tarnish like normal brass and resists corrosion, and is purported to be somewhat smoother than brass, for whatever benefits that may offer in aiding extraction or insertion into a firearm's chamber; It is commonly seen on handgun cartridges geared towards self-defense. Aluminum (seen on cartridge 4 above) is cheaper to manufacture than brass and more resistant to corrosion than steel, creating a fair balance of function and affordability.
Case Shape
The base of a metallic casing may feature a rim, or small shoulder of metal around the circumference. Rims are visible on cartridges 6, 7, 11, and 12, where they serve the function of indexing the cartridge in the chamber (preventing it from entering too far into the barrel), and on cartridges 8 and 9, where they also contain the primer.
The remaining cartridges (1, 2, 3, 4, 5, and 10) have lips in the base of the cartridge which the firearms they are used in grab onto to manipulate the cartridge.
Notice also the short section of the case of cartridge 10 which has been reduced in diameter to fit the bullet. The sloped portion of this reduction is called the shoulder, and the straight portion containing the bullet the neck. These shouldered cases allow a greater volume of powder to propel a smaller bullet to higher velocities.
Functions of Ammunition
Bullet Design
The Spitzer Bullet
Visible above in cartridge 10, the spitzer bullet comes to a tapered point rather than having a rounded front like the bullets of handgun cartridges 1-5. This point offers better ballistic performance and reduced air resistance over the longer distances that rifles are used at. Handgun cartridges almost never feature spitzer pointed bullets because their effectiveness relies upon mass, rather than velocity, at very short ranges - the bullets of cartridges 1-5 are all more than twice as heavy as the bullet of cartridge 10 for this reason.
The Hollow Point Bullet
Hollow point bullets, visible in cartridges 1, 2, 6, and 8, are designed as stated above to expand upon impacting a target. This makes hollow point bullets an ideal choice for self-defense due to a number of important characteristics. Firstly, as they expand they slow down considerably, reducing the likelihood that they will penetrate their target completely and continue on to strike and injure bystanders. Secondly, this expansion and ensuing reduction in velocity ensures these bullets expend all of their energy within the intended target, rather than continuing through and wasting this energy, allowing these bullets to more reliably incapacitate an attacking person or animal.
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| A variety of jacketed and semi-jacketed hollow point bullets |
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| An expanded Speer Gold Dot hollow point bullet, bottom-right in the above image. Image Source: Reddit user directionofk |
Misconceptions
Teflon-coated bullets
Developed by law enforcement personnel for police agencies in search of bullets better suited to penetrating hardened barriers such as car windshields, Teflon-coated bullets garnered controversy as bullets designed to penetrate the armored vests worn by police officers - dubbed "cop-killer" bullets by some. Two important things to note concerning the Teflon-coated bullet (dubbed KTW, after the initials of its inventors), are that A. the Teflon coating was immaterial to their increased barrier penetration ability, which was provided by the bullet's composition of hardened brass with a steel core - the coating was meant to preserve the life of the barrels the bullets were fired through, which were damaged by the hardened bullet, and B. that the KTW round was only ever sold in minute quantities to police agencies, not to the public. Armor piercing ammunition is furthermore illegal for sale to non-law enforcement or military personnel.
Hollow point bullets versus Kevlar body armor
Some controversy has also arisen concerning hollow point bullets and their efficacy against the Kevlar bullet-proof vests worn by law enforcement officers. Bullets such as Winchester's Black Talon, an early modern hollow point, have also been dubbed "cop-killer" bullets by gun control advocates for this reason. Hollow point bullets are designed to expand upon impacting a target and stop within a short distance, rather than traveling through it, making them one of the least effective bullet designs available if armor penetration is the desired effect.
Conclusion
The advent of the self-contained metallic cartridge opened the way for numerous innovations in firearms design by solving the issue of slow, difficult loading by combining the necessary elements of firing a gun - projectile, powder, and primer - into a single unit, easily manipulable by the operator.
In the intervening time, countless bullet and case designs have been developed and experimented with, some meeting greater success than others, but all designed with a specific purpose in mind, and with pronounced variances between them.
