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Unlocking 5.7×28 Velocity: How Barrel Length Impacts Performance

The 5.7x28mm cartridge, a high-velocity, small-caliber round, has garnered significant attention in both military and civilian shooting communities. A crucial aspect of its performance is the relationship between 5.7×28 velocity vs barrel length. Understanding this relationship is paramount for optimizing accuracy, effective range, and overall ballistic performance. This article provides a comprehensive exploration of how barrel length influences the velocity of the 5.7×28 round, offering insights for shooters, reloaders, and firearm enthusiasts seeking to maximize the potential of this unique cartridge. We’ll delve into the physics behind the phenomenon, examine real-world data, and discuss the implications for various applications.

Understanding the 5.7×28 Cartridge and its Ballistic Profile

The 5.7x28mm cartridge was developed by FN Herstal in the late 1980s and early 1990s, primarily for use in the FN P90 personal defense weapon (PDW) and the FN Five-seveN pistol. Its design prioritizes a flat trajectory, high velocity, and enhanced armor-piercing capabilities compared to traditional pistol cartridges like 9mm. The small diameter and lightweight projectile contribute to its high velocity, which is crucial for achieving its intended ballistic effects.

The cartridge utilizes a bottlenecked case design, allowing it to hold a relatively large powder charge for its size. This, combined with the lightweight bullet, enables it to achieve velocities significantly higher than many other handgun rounds. However, achieving optimal velocity and consistent performance requires careful consideration of various factors, including barrel length, ammunition type, and environmental conditions.

The Physics of Velocity and Barrel Length

The relationship between barrel length and projectile velocity is governed by fundamental physics principles. When a cartridge is fired, the expanding gases from the burning propellant exert pressure behind the bullet, accelerating it down the barrel. The longer the barrel, the longer these gases act on the bullet, theoretically increasing its velocity. However, this relationship isn’t linear. There’s a point of diminishing returns where the friction between the bullet and the barrel, along with the cooling and expansion of the gases, begins to outweigh the benefits of increased barrel length.

Several factors influence this point of diminishing returns, including:

Propellant Type: Different propellants burn at different rates and produce varying amounts of gas. Some propellants are optimized for shorter barrels, while others are designed for longer barrels.
Bullet Weight and Design: Heavier bullets generally require more energy to accelerate, and longer barrels may be needed to achieve optimal velocity. The bullet’s bearing surface (the area in contact with the barrel) also affects friction and velocity.
Chamber Pressure: Higher chamber pressures can generate more gas and potentially increase velocity, but they also increase stress on the firearm.
Barrel Condition: A smooth, clean barrel will generally produce higher velocities than a rough, fouled barrel due to reduced friction.

Understanding these factors is crucial for predicting how barrel length will affect the velocity of a specific 5.7×28 load. In general, shorter barrels will result in lower velocities, while longer barrels may result in higher velocities, up to a certain point.

5.7×28 Velocity vs. Barrel Length: A Detailed Examination

Let’s examine the specific impact of barrel length on 5.7×28 velocity. This cartridge is often used in firearms with varying barrel lengths, ranging from the short barrels of pistols like the FN Five-seveN (around 4.8 inches) to the longer barrels of carbines like the FN PS90 (around 16 inches).

Short Barrels (4-6 inches)

In pistols with barrel lengths around 4-6 inches, the 5.7×28 cartridge typically produces velocities in the range of 1800-2100 feet per second (fps), depending on the specific ammunition. While this is still a respectable velocity, it’s significantly lower than what can be achieved with longer barrels. The shorter barrel limits the amount of time the expanding gases have to act on the bullet, resulting in incomplete propellant combustion and reduced energy transfer.

However, short barrels offer advantages in terms of concealability and maneuverability, making them popular for personal defense. Shooters choosing a short-barreled 5.7×28 pistol should be aware of the velocity limitations and select ammunition accordingly. Ammunition specifically designed for shorter barrels may use faster-burning propellants to maximize velocity within the limited barrel length.

Medium Barrels (8-12 inches)

Firearms with barrel lengths in the 8-12 inch range offer a compromise between velocity and maneuverability. In this barrel length range, the 5.7×28 cartridge can achieve velocities of around 2100-2300 fps. The increased barrel length allows for more complete propellant combustion and more efficient energy transfer to the bullet.

This barrel length is often found in pistol-caliber carbines (PCCs) or SBRs (short-barreled rifles) chambered in 5.7×28. These firearms offer improved accuracy and range compared to pistols, while still being relatively compact and easy to handle.

Long Barrels (16 inches and longer)

The FN PS90, with its 16-inch barrel, is a prime example of a firearm designed to maximize the velocity potential of the 5.7×28 cartridge. In this barrel length, the 5.7×28 can achieve velocities of 2400-2600 fps or even higher, depending on the ammunition. The longer barrel allows for nearly complete propellant combustion and optimal energy transfer, resulting in a flatter trajectory, increased range, and greater terminal effectiveness.

However, longer barrels also increase the overall size and weight of the firearm, which may be a disadvantage in some situations. The 16-inch barrel length of the PS90 is often considered the optimal balance between velocity and handling for the 5.7×28 cartridge.

Ammunition Selection and its Influence

Ammunition selection plays a crucial role in determining the velocity of the 5.7×28 cartridge, regardless of barrel length. Different manufacturers load their ammunition to varying specifications, using different propellants, bullet weights, and bullet designs. Some ammunition is specifically designed for optimal performance in short barrels, while others are optimized for longer barrels.

For example, lighter bullets generally achieve higher velocities than heavier bullets, but they may also have lower ballistic coefficients and be more susceptible to wind drift. Ammunition with faster-burning propellants may be better suited for shorter barrels, while ammunition with slower-burning propellants may be better suited for longer barrels.

It’s essential to consult the ammunition manufacturer’s specifications and test different loads in your firearm to determine which ammunition provides the best combination of velocity, accuracy, and reliability. Chronographs are valuable tools for measuring the actual velocity of ammunition in your firearm.

Real-World Testing and Data Analysis

Numerous independent tests have been conducted to measure the velocity of the 5.7×28 cartridge in different barrel lengths. These tests generally confirm the trend of increasing velocity with increasing barrel length, up to a certain point. However, the specific velocities achieved can vary depending on the ammunition used, the firearm used, and the testing conditions.

One notable test, conducted by Small Arms Review, compared the velocity of several different 5.7×28 loads in barrel lengths ranging from 4.8 inches to 16 inches. The results showed a consistent increase in velocity with increasing barrel length, with the 16-inch barrel achieving velocities approximately 300-400 fps higher than the 4.8-inch barrel. This test also highlighted the significant variations in velocity between different ammunition types.

Another test, conducted by Shooting Illustrated, focused on the accuracy and terminal performance of the 5.7×28 cartridge in different barrel lengths. While the test primarily focused on accuracy, it also measured velocity and found similar trends to the Small Arms Review test.

These tests underscore the importance of conducting your own testing to determine the optimal ammunition and barrel length combination for your specific needs. While published data can provide a general guideline, it’s no substitute for real-world testing.

Practical Implications for Shooters

Understanding the relationship between 5.7×28 velocity and barrel length has several practical implications for shooters:

Ammunition Selection: Choose ammunition that is optimized for your barrel length. If you have a short-barreled pistol, select ammunition with faster-burning propellants. If you have a longer-barreled carbine, select ammunition with slower-burning propellants.
Accuracy Considerations: Higher velocity can contribute to a flatter trajectory and improved accuracy, especially at longer ranges. If accuracy is a primary concern, consider using a longer barrel.
Terminal Performance: Velocity is a key factor in determining the terminal performance of a bullet. Higher velocity generally results in greater energy transfer and more effective wound cavities. If terminal performance is a primary concern, consider using a longer barrel and ammunition designed for expansion or fragmentation.
Legal Restrictions: Be aware of any legal restrictions on barrel length in your jurisdiction. NFA regulations in the United States, for example, regulate short-barreled rifles (SBRs) and require registration and tax stamps.

The FN Five-seveN: A Closer Look

The FN Five-seveN pistol is a semi-automatic handgun chambered in 5.7x28mm. Designed by FN Herstal, it’s known for its lightweight polymer frame, high-capacity magazine, and the high-velocity 5.7x28mm cartridge. Its primary function is as a sidearm for military and law enforcement personnel, but it has also gained popularity among civilian shooters for sport and self-defense.

The Five-seveN’s design emphasizes reduced recoil and increased accuracy compared to traditional pistol cartridges. The 5.7x28mm cartridge’s flat trajectory allows for easier aiming at longer distances, while the pistol’s lightweight construction makes it comfortable to carry. The high-capacity magazine (typically 20 rounds) provides a significant advantage in a defensive situation.

Key Features of the FN Five-seveN

The FN Five-seveN boasts several features that contribute to its performance and popularity:

Lightweight Polymer Frame: The polymer frame significantly reduces the pistol’s overall weight, making it easier to carry and handle. This is particularly important for military and law enforcement personnel who may carry the pistol for extended periods. The polymer construction is also resistant to corrosion and wear.
High-Capacity Magazine: The standard magazine holds 20 rounds of 5.7x28mm ammunition, providing a significant advantage in a defensive situation. An extended 30-round magazine is also available.
Ambidextrous Controls: The Five-seveN features ambidextrous magazine release and slide stop levers, making it suitable for both right-handed and left-handed shooters.
Adjustable Sights: The pistol is equipped with adjustable sights, allowing the shooter to fine-tune the point of impact. Some models also feature tritium night sights for enhanced visibility in low-light conditions.
Accessory Rail: The Five-seveN typically includes an accessory rail located beneath the barrel, allowing the attachment of lights, lasers, or other accessories.
Internal Hammer: The internal hammer design contributes to a smooth trigger pull and enhanced reliability.
Rotating Barrel Locking System: This system enhances accuracy and reduces recoil by better managing the forces generated during firing.

Advantages of the FN Five-seveN and 5.7×28 Combination

The FN Five-seveN and 5.7×28 combination offers several significant advantages:

Reduced Recoil: The 5.7×28 cartridge produces significantly less recoil than traditional pistol cartridges like 9mm or .45 ACP, allowing for faster follow-up shots and improved accuracy. Users frequently report the ease of controlling the firearm.
High Capacity: The high-capacity magazine provides a significant advantage in a defensive situation, allowing the shooter to engage multiple targets without needing to reload frequently.
Flat Trajectory: The 5.7×28 cartridge’s flat trajectory makes it easier to aim at longer distances, reducing the need for significant holdover.
Armor Penetration: Certain 5.7×28 loads are capable of penetrating soft body armor, making them a popular choice for law enforcement and military personnel.
Lightweight: The pistol’s lightweight construction makes it comfortable to carry and handle.

Our analysis reveals these key benefits make the Five-seveN a compelling option for those seeking a high-performance handgun.

A Critical Look: Reviewing the FN Five-seveN

The FN Five-seveN is a unique and controversial handgun. It offers several advantages, but it also has some drawbacks. This review provides a balanced perspective on the pistol, based on practical usage and expert opinions.

User Experience and Usability: The Five-seveN is generally considered to be easy to use, thanks to its lightweight construction, comfortable grip, and simple controls. The ambidextrous controls are a welcome feature for left-handed shooters. However, some users find the grip to be too large, especially those with smaller hands. The trigger pull is generally smooth, but it can be somewhat heavy on some models.

Performance and Effectiveness: The Five-seveN delivers on its promise of reduced recoil and improved accuracy. The 5.7×28 cartridge’s flat trajectory makes it easy to hit targets at longer distances. The pistol is also reliable, with few reported malfunctions. However, the terminal performance of the 5.7×28 cartridge has been a subject of debate. While some loads are capable of penetrating soft body armor, others may not produce sufficient wound cavities to quickly incapacitate an attacker.

Pros:

Low Recoil: Allows for fast follow-up shots and improved accuracy.
High Capacity: Provides a significant advantage in a defensive situation.
Flat Trajectory: Makes it easier to hit targets at longer distances.
Lightweight: Comfortable to carry and handle.
Reliable: Few reported malfunctions.

Cons/Limitations:

Grip Size: May be too large for some users.
Terminal Performance: Some loads may not produce sufficient wound cavities.
Ammunition Cost: 5.7×28 ammunition is generally more expensive than other pistol cartridges.
Controversial Cartridge: The 5.7×28 cartridge has been criticized for its potential to penetrate soft body armor.

Ideal User Profile: The FN Five-seveN is best suited for shooters who prioritize low recoil, high capacity, and accuracy. It’s a good choice for law enforcement and military personnel, as well as civilian shooters who want a reliable and accurate handgun for self-defense or sport.

Key Alternatives: The Glock 17 and the Smith & Wesson M&P are popular alternatives to the FN Five-seveN. These pistols are chambered in 9mm and offer similar features, but they have different recoil characteristics and ammunition costs.

Expert Overall Verdict & Recommendation: The FN Five-seveN is a unique and capable handgun that offers several advantages. While it has some drawbacks, its strengths outweigh its weaknesses for many shooters. If you’re looking for a low-recoil, high-capacity, and accurate handgun, the Five-seveN is definitely worth considering. We recommend carefully researching different ammunition options to find the best load for your specific needs.

The Final Shot: Optimizing 5.7×28 Performance

In conclusion, the relationship between 5.7×28 velocity and barrel length is a critical factor in optimizing the performance of this unique cartridge. While longer barrels generally produce higher velocities, the specific velocities achieved depend on a variety of factors, including ammunition selection, firearm design, and environmental conditions. By understanding these factors and conducting your own testing, you can make informed decisions about ammunition and barrel length to maximize the accuracy, range, and terminal effectiveness of your 5.7×28 firearm. Share your experiences with 5.7×28 barrel length and velocity in the comments below; your insights contribute to a more complete understanding of this fascinating topic.