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image depicting FMJ ammo on left and a hollow point bullet on the right
FMJ bullets are shown on the left, while a hollow point bullet is on the right.

If you’re new to the world of shooting, you might find yourself quickly bogged down with new vocabulary. Some of the most important verbiage will necessarily concern the type of ammunition you use. You may be familiar with the term “Full Metal Jacket” (FMJ) thanks to a certain film. But what, exactly, is FMJ ammo? What are its applications and limitations? Read our article to learn more.  

What is FMJ Ammo?

Full Metal Jacket (FMJ)  ammunition is a type of bullet commonly used in target practice. Its defining feature is a bullet casing that encloses the entire bullet except for its base. The bullet itself is typically made of a lead core surrounded by a copper or other metal alloy jacket. This jacket covers the entire length of the bullet, hence the term “full metal jacket.”

FMJ vs TMJ Ammo

TMJ stands for “Total Metal Jacket,” which is a variation of FMJ ammunition. While both TMJ and FMJ bullets feature a metal jacket encasing the core of the bullet, there are some differences between the two.

The main distinction between TMJ and FMJ ammunition lies in how the metal jacket is applied to the bullet. In FMJ bullets, the jacket typically covers the entire bullet except for the base, leaving the lead core exposed at the base. On the other hand, TMJ bullets have a thicker jacket that completely encapsulates the lead core, including the base, leaving no exposed lead.

TMJ bullets perform similarly to FMJ rounds, with even greater reduction in residue build up thanks to the fully encapsulated bullet. 

When Is FMJ Ammo Used? 

FMJ ammo is typically used in cases of rapid, high-volume fire. It is ideal when practicing at the range, offering several advantages over other types of ammo: 

FMJ Ammo is Cheaper

Full metal jacket ammo  is often more affordable compared to other types of ammunition, such as hollow points or specialized hunting rounds. This is primarily because FMJ bullets have a simpler design and are less expensive to manufacture. As a result, shooters who engage in regular target practice or training sessions may prefer FMJ ammo due to its lower cost per round.

Full Metal Jacket Ammo is Reliable

FMJ ammunition is known for its reliability and consistency. The solid metal jacket surrounding the lead core provides structural integrity to the bullet, reducing the likelihood of deformation or fragmentation during firing. It also means far less residue than occurs with exposed lead bullets. This makes FMJ rounds ideal for high-volume shooting scenarios, such as military training exercises or competitive shooting events.

Feed and Function

FMJ ammunition typically feeds and functions well in a wide variety of firearms. The smooth, rounded profile of FMJ bullets reduces the likelihood of feeding jams or malfunctions, making them a popular choice for semi-automatic pistols and rifles.

Consistency

FMJ ammunition tends to offer consistent ballistic performance from round to round. This consistency is beneficial for shooters who require predictable accuracy and performance, whether for competitive shooting or professional applications.

FMJ vs Hollow Point Ammunition

Unlike FMJ ammo, hollow point ammunition has a small cavity at the tip of the bullet. This seemingly insignificant feature has huge implications. Specifically, it allows the bullet to expand and slow on impact. A weapon utilizing hollow point ammunition produces a larger and potentially more deadly wound, which is why these bullets are used for self defense weapons. The slowing of the bullet is also important for the safety of bystanders (see below). 

Additionally, hollow point ammunition is typically coated with a nickel-brass plate, which increases the bullet’s resistance to corrosion. If you intend to carry daily, this is an important consideration. 

a hollow point bullet after it has been fired
A hollow point bullet after it has been fired. These bullets expand on impact to increase damage potential and reduce the risk of over-penetration.

Why Do You Not Use FMJ Ammo Outside the Range?

While FMJ ammunition is effective for target shooting and military use, it’s generally not recommended for self-defense or hunting purposes. This is because FMJ bullets tend to over-penetrate, meaning they can pass through a target and potentially cause unintended harm to bystanders or property.

One of the primary rules of responsible gun ownership is knowing your target and what lies beyond it. This is impossible with FMJ ammo, since you cannot be sure your bullet will not overpenetrate and possibly hit something or someone behind it. 

In self-defense situations, hollow point ammunition is preferred for its ability to expand upon impact, delivering more energy to the target and reducing the risk of over-penetration. Similarly, for hunting, ammunition designed to expand or fragment upon impact is preferred to ensure a clean and ethical kill.

Do You Always Use Full Metal Jacket Ammunition When Practicing?

Certainly not! While FMJ ammo is preferable for training or recreational purposes, you should always test your self-defense ammo in the safe, controlled environment of a gun range. Unlike full metal jacket bullets, hollow points vary in size and may not always work with your preferred firearm. You will want to be sure the ammo is compatible with your concealed carry before you rely on it for self defense. 

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