Popular Ammunition Basics: A Guide To Calibers, Sizes and Types

Any firearm owner or enthusiast must understand the basics of projectiles and cartridges. Having knowledge on projectiles, sizes and types is important if you are a pro or new to this. This expertise will ensure you select the right ammunition for your firearms for optimal safety and performance. It also allows you to better understand ballistics terminology and make informed choices when purchasing ammo.

This guide will provide a comprehensive overview of projectile and cartridge basics. We'll define key terms, break down common calibers along with their pros and cons, explain different projectile types, detail shotgun shell varieties and even look inside cartridges at their components. By the end, you'll be a projectile pro!

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Projectile Sizes and Calibers Basics

The "caliber" of a projectile essentially refers to its diameter. This measurement matches the diameter of the gun barrel that the projectile is designed for. Using properly calibrated ammunition ensures a tight seal and therefore allows the explosive gases to propel the projectile effectively through the barrel. Small variations in projectile size can impact velocity, accuracy and more.

It's also important to distinguish between "projectile" and "cartridge" when talking about ammo. The term "projectile" specifically refers to the metal projectile that is fired from the barrel towards a target. The entire unit of ammunition that holds the projectile, casing, gunpowder and primer is called the cartridge.

Here's a breakdown of the key pieces inside a projectile cartridge:

• Projectile- usually made of lead, copper or other metal alloy
• Casing - The metal cylinder that contains all the other components, usually made of brass, steel, copper or aluminum
• Propellant - this is the explosive material that provides the energy when ignited to propel the bullet
• Primer - The ignition component, usually made of shock-sensitive explosive, that explodes when struck by the firing pin.

Rimfire vs. Centerfire Cartridges

There are two main types of cartridges - rimfire and centerfire. The key difference lies in the location of the priming compound.

Rimfire cartridges have the primer contained inside the rim of the cartridge casing. When you look at a rimfire round, you'll see the rim is indented. The firing pin strikes this rim region to ignite the primer. Rimfire rounds are extremely cheap, usually costing just a few cents per cartridge. The .22 Long Rifle (LR) is by far the most popular rimfire caliber. However, rimfire rounds are less reliable and can misfire more frequently.

Centerfire cartridges have the primer located in the center of the casing base. You'll see a distinct circular indentation there. When the firing pin strikes this central primer, the spark ignites the gunpowder inside to fire the projectile outwards. Centerfire ammunition is more reliable and versatile. However, these rounds are more costly because manufacturing the central primer involves additional steps.

Popular projectile Calibers

Now let's explore some of the most widely used projectile calibers, looking at the pros and cons of each:

• Pros: Extremely affordable, very little recoil, great for plinking and small game hunting
• Cons: Not suitable for self-defense applications

The .22 LR (Long Rifle) rimfire round is by far the most commonly fired cartridge. It has almost no recoil, making it perfect for new shooters. The minimal noise and cheap ammo also make it very popular for casual "plinking" practice.

While .22 LR guns can kill small animals, the projectile lacks adequate stopping power for self defense use. Tiny .22 rounds can struggle to reliably penetrate deeply enough to hit vital organs. However, low cost and accessibility means .22 is one of the most popular firearms available..

Overall, the .22 LR is best suited for affordable target practice and hunting small game like rabbits, squirrels and birds. The low recoil builds confidence for beginners. And an afternoon plinking through boxes of .22 ammo is still fun for experienced shooters.

.380 ACP

• Pros: Suitable for concealed carry pistols, relatively low recoil
• Cons: Less stopping power than larger calibers, limited effectiveness beyond close distances

The .380 ACP (Automatic Colt Pistol) round is a popular option for compact concealed carry handguns. The small size and low recoil enables comfortable carry. Modern hollow point loads also improve the .380's stopping ability compared to full metal jackets which should never be used as a defensive ammunition.

However, the .380 ACP sits at the bare minimum recommendation for defensive calibers. This caliber offers. short offers adequate stopping power only at very close quarters. Penetration and expansion rapidly decline past 7-10 yards.

With new tiny "pocket pistol" options on the market, the .380 ACP has seen major growth thanks to its easy concealability. But it still resides at the bottom tier of what experts consider adequate for self defense rounds. Proper shot placement becomes critical for neutralizing threats with the .380.

9mm

• Pros: Proven stopping power, NATO standard round, high availability
• Cons: Potential over-penetration in self-defense situations

The 9x19mm Parabellum or 9mm Luger is the world's most popular handgun cartridge. With over a century of combat usage and development, the 9mm strikes a superb balance of stopping effectiveness, recoil control, ammunition capacity and affordability.

It is the standard handgun caliber for NATO members, U.S. law enforcement agencies and military forces globally. Advancements in ammunition have enabled properly expanded 9mm hollow points to achieve adequate penetration and stopping power in defensive shootings.

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The 9mm also enables high capacity pistol designs thanks to its slim profile cartridge size. While no round is perfect across all measures, the 9mm hits a versatile sweet spot, making it a logical default choice suitable for many types of handgun users and use cases

.40 S&W

• Pros: Higher stopping power than 9mm, preferred by many law enforcement agencies
• Cons: Increased recoil, lower magazine capacity than 9mm equivalents

Developed as an alternative to the 10mm, the .40 S&W was designed in a joint effort between Winchester and Smith & Wesson to better meet the needs of law enforcement. Following a deadly 1986 shootout the FBI sought a cartridge with better terminal ballistics than the 9mm.

The .40 S&W provided a shortened 10mm case pushing a 180 grain projectile at 950 fps. This delivered superior stopping power compared to 9mm in a more controllable package. The .40 caliber round soon became popular with police forces and federal agencies across the United States.

However, the snappier recoil of the .40 S&W reduces rapid fire accuracy. The larger diameter projectiles also mean reduced magazine capacities - often 2-3 rounds less than comparable 9mm models. Although many major law enforcement agencies adopted the .40 S&W in the 1990s and continue using it today, there has been a recent trend back towards the more shootable 9mm cartridge.

Police forces have increasingly favored the 9mm as advances in defensive ammunition enhance its accuracy and fire volume over marginal per-shot power gains. Still, the .40 S&W remains a highly popular option among those seeking a compromise between the 9mm and .45 ACP.

.45 ACP

• Pros: Iconic history with 1911 platform, superior stopping power
• Cons: Heavy recoil, low magazine capacity

The .45 ACP round is practically synonymous with the legendary M1911 pistol designed by John Moses Browning in the early 1900's. When the U.S. Army was searching for a new sidearm cartridge with better stopping power, Browning paired his iconic 1911 platform with the massive .45 ACP projectile he developed. The Army quickly adopted the combination as its standard issue sidearm for decades thanks to the .45 ACP's reputation as a "man stopper" round.

Today, the .45 ACP lives on as a highly popular self defense and hunting cartridge, though most modern shooters use it predominantly in 1911-style pistols out of tradition. The 230 grain projectiles require heavy springs and slides to soak up their stout recoil. This leads to lower magazine capacities - typically 8+1 rounds in 1911 models.

While the .45 ACP maintains a strong nostalgic following, more people now often opt for the milder shooting traits and higher capacities of 9mm platforms. Still, the "forty-five" holds an iconic place in history and continues to serve those seeking its substantial knockdown power.

.38 Special & .357 Magnum

• Pros: At home in revolvers, .357 Magnum also shoots .38 Special
• Cons: Generally lower ammo capacity in revolvers, challenging recoil

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Originally designed as a black powder cartridge, the .38 Special gained immense popularity as an effective police revolver cartridge in the early 20th century. It continues to be a prolific revolver round today for self defense, target shooting and taking small game. The longer .357 Magnum arrived later firing a heavier projectile at substantially higher velocities out of revolver barrels. This makes the .357 one of the most formidable magnum handgun rounds available.

A major advantage of the .357 Magnum is its ability to also fire the shorter .38 Special cartridge. However, the long revolver cylinders required for .357 cartridges still typically only hold 5-6 rounds. While adequate for most defensive scenarios, this pales in comparison to semi-automatic handgun capacities.

Shooters must also contend with punishing muzzle blast and recoil from lightweight revolvers, especially when firing full power .357 Magnum ammo. Still, both the .38 Special and .357 Magnum rounds have earned places in history thanks to their versatility and home in rugged revolver platforms.

7.62x39mm

• Pros: Iconic AK-47 round, good stopping power.
• Cons: Not as accurate at long ranges as high velocity rounds.

Originally developed in the 1940's Soviet Union, the 7.62x39mm cartridge first saw widespread use in the AK-47 assault rifle. This intermediate power round strikes a nice balance between shot control and stopping effectiveness for semi-automatic military firearms.

It generally fires a 123 grain mild steel jacketed projectile at a velocity around 2300 fps when using a 16-inch barrel. This 7.62mm round does not shoot as flat at longer ranges compared to smaller, faster calibers like the 5.56x45mm.

However, it remains extremely popular worldwide as the standard ammunition for iconic AK-47 derivative rifles. While 7.62x39mm ammo remains available, its accessibility has decreased somewhat since the onset of the Ukraine war, yet it continues to be quite affordable due to large cold war stockpiles.

.223/5.56x45mm

• Pros: High velocity round, light recoil
• Cons: Controversy exists around stopping effectiveness in combat engagements

These two extremely similar projectile cartridges - .223 Remington and 5.56x45mm NATO - feature in some of the most ubiquitous military rifles around the world, including the M16, M4 and AR-15 platforms.

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Despite their small bottlenecked shape, these cartridges use fast-burning propellant to push the 55-77 grain projectiles at velocities over 3000 feet per second from standard rifle barrels. This gives the .22 caliber rounds excellent accuracy and flat shooting abilities out to 500+ Meters.

However, there is debate around how effectively such lightweight, hyper-velocity projectiles stop targets even with fragmentation. Originally optimized for lightly equipped fighters, recent modernizations in ammunition technology have enhanced the terminal performance of both .223 and 5.56mm rounds. Still some argue these fast little projectiles lack adequate stopping power for hunting medium sized game or against determined attackers high on adrenaline or drugs.

What isn't up for debate however is that the mild shooting traits and high capacity of .223/5.56mm firearms make it an ideal caliber for defensive patrol, military operations and competitive shooting where rapid, accurate follow up shots are required during high stress encounters.

.308/7.62x51mm

• Pros: Hard hitting round ideal for hunting and tactical applications
• Cons: Punishing recoil, expensive ammunition

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With nearly identical dimensions, the .308 Winchester and 7.62x51mm NATO cartridges represent two sides of the same highly versatile rifle caliber. Civilian hunters and competitive target shooters favor the commercial .308 Winchester round for its accuracy and availability. Meanwhile, global militaries and law enforcement snipers utilize the "7.62x51mm NATO" due to its full power loadings and superior barrier penetration.

Both calibers fire heavier 150-200 grain projectiles at high velocities thanks to an efficient powder capacity and tapered body shape. This gives the ammunition outstanding stopping capabilities and consistent precision out to 800+ yards in capable hands.

The .308 and 7.62x51mm NATO does produce noticeable recoil however, especially during rapid fire strings. And the large magnum rounds cost more than intermediate calibers. However, for hunters pursuing big game or tactical teams needing decisive stopping power at a distance, the .308/7.62mm delivers terminal ballistics that are hard to beat.

.50 BMG

• Pros: Extreme range (confirmed kills beyond 2000m)
• Cons: Impractical for civilian ownership, expensive ammunition

Developed for heavy machine guns in the early 20th century, the .50 BMG fires an enormous 0.5 inch diameter projectile weighing over 660 grains. Early applications saw the round utilized for long range anti-aircraft defense. Today, the "Fifty" continues serving in specialized sniper and anti-material rifles.

Enormous powder capacity allows the 24mm long cartridges to propel these substantial projectiles downrange at velocities exceeding 3000 fps. This extreme combination of mass and speed gives the .50 BMG unmatched accuracy at distances out to 2000+ meters. The sheer energy and penetration also enables defeating light armor.

However, virtually every aspect of the .50 BMG including the firearms themselves are heavily regulated. The extreme recoil and deafening blast make .50 caliber rifles seemingly impractical for average recreational shooters, yet there are users who maintain these firearms in their personal collections—not in Mil-Spec versions, but in consumer-grade configurations.. The ammunition is also prohibitively expensive. These factors relegate the mighty .50 BMG to exclusive use by elite military units and the most dedicated long range precision shooters.

Common projectile Types and Their Definitions

Now that we've covered some popular projectile sizes, let's shift gears to talking about projectile types and configurations. Here are some of the most common:

Full Metal Jacket (FMJ) - Full Metal Jacket (FMJ) projectiles feature a soft core, typically made of lead, encased entirely in a harder shell, usually copper. FMJ projectiles maintain their shape and penetrate deeply. However they provide minimal expansion or stopping power.

Hollow Point (HP) - Hollow points have a pitted nose which enables the projectile to expand upon impact. This creates larger wound channels and greater stopping power. For this reason, hollow points are recommended for most self-defense applications.

Open Tip Match (OTM) - The Open Tip projectile features a hollow point-like opening in its tip. However, this larger opening is more a byproduct of its manufacturing process rather than intentional design. Open Tip projectiles provide superior aerodynamic qualities and consistency for long distance shooting.

Ballistic Tip - Ballistic tip projectiles attempt to merge the flight characteristics of FMJ rounds with the expanding traits of hollow points. They feature a lightweight plastic tip attached to a hollow cavity projectile. The tip improves aerodynamics while the hollow point enhances expansion.

Soft Point - With exposed lead at their tips soft point projectiles achieve controlled expansion via their softer metals. This helps improve stopping effectiveness compared to enclosed FMJ rounds.

There are certainly many more specialty projectile types but these comprise the most common.

Types of Shotgun Ammunition Explained

When it comes to shotguns, the 12 gauge is by far the most popular bore size. Unlike rifles and handguns, shotguns enjoy immense ammunition versatility through the use of different shell types:

Birdshot - Best for hunting fowl and skeet shooting. Birdshot consists of dozens of tiny lead pellets packed into each shotgun shell. This allows the shot to spread out emerging from the barrel to strike flying targets.

Buckshot - The go-to ammunition choice for defensive shotgun use is 00 ("double aught") buckshot. Instead of tiny pellets, buckshot contains 8-9 large ~9mm diameter balls in each shell, enabling decisive stopping power at close quarters.

Slug - Shotgun slugs are solid metal projectiles weighing approximately 1 ounce. Slugs are intended for single projectile accuracy and extended range (100+ yards) shooting rather than a spreading shot pattern. They bring massive penetration capabilities to the shotgun platform.

Final Thoughts

We've covered a ton of ground discussing different projectile and shotshell types, common calibers, cartridge compositions and more. The most important takeaway is understanding the basics of how ammunition components and specifications impact real world effectiveness. Apply this knowledge responsibly to purchase the ideal ammunition to match your individual firearms and use case. Stay safe and continue growing your ballistics knowledge!

FAQs

What is the difference between a projectile and a cartridge?

The projectile refers specifically to the metal projectile that exits from the barrel towards the target. The complete ammunition unit including projectile, casing, gunpowder and primer is called the cartridge.

What is the difference between a projectile and a cartridge?

The projectile refers specifically to the metal projectile that exits from the barrel towards the target. The complete ammunition unit including projectile, casing, gunpowder and primer is called the cartridge.

Can you use .223 ammunition in a 5.56 rifle?

Yes, .223 Remington ammo can safely fire from a 5.56 NATO chambered rifle. The external dimensions are nearly identical but the 5.56 operates at higher pressures. Using the lower pressure .223 in a 5.56 firearm is fine.

What shotgun shell is best for home defense?

00 ("double aught") buckshot is the recommended ammo for defensive use of shotguns. The nine pellets are each about .33" diameter and provide decisive stopping power at close ranges.

What is the difference between rimfire and centerfire ammunition?

Rimfire cartridges have the priming compound inside the rim while centerfire cartridges have a separate primer seated centrally inside the casing base. Rimfire ammo tends to be less expensive while centerfire rounds are more reliable.

Why choose hollow point projectiles for self-defense?

Hollow points reliably expand upon impact to create larger wound channels and disrupt vital organs. This prevents overpenetration and provides superior stopping effectiveness compared to full metal jacket rounds.

What is the best all-around handgun caliber?

The 9mm cartridge provides the best balance of stopping power, recoil management, ammunition capacity and affordability. The NATO standard 9x19mm is arguably the most versatile handgun caliber available today.