What Assault Rifle Does the Army Use?

Table of Contents

1. Introduction
2. The M4A1 Carbine: The Current Standard
3. The NGSW Program: Why the Army is Changing
4. The XM7: The Army’s New Assault Rifle
5. The 6.8x51mm Common Cartridge
6. The XM157 Fire Control System
7. Comparing the Platforms: M4A1 vs. XM7
8. Maintaining the Edge: Training and Gear
9. The Civilian Version: SIG Sauer MCX Spear
10. The Future of Army Small Arms
11. Conclusion
12. FAQ

Introduction

The United States Army is currently in the middle of the most significant small arms transition in over half a century. For decades, the answer to what assault rifle the Army uses was simple: the M16 or the M4 Carbine. Today, that answer is more complex. While the M4A1 remains the standard-issue workhorse for the majority of the force, the Army has officially begun fielding its successor—the SIG Sauer XM7. At Crate Club, we track these shifts closely because the gear used by the front-line operator eventually dictates the standards for the entire tactical industry. This transition represents a shift in philosophy from the lightweight, high-volume fire of the 5.56 NATO round to the increased range and punch of the 6.8mm Common Cartridge. This guide covers the current state of the Army’s primary small arms, the technical specs of the new XM7, and what this means for the future of tactical gear.

Quick Answer: The U.S. Army currently uses the M4A1 Carbine as its primary service rifle, but it is officially transitioning to the XM7 (formerly the XM5) as part of the Next Generation Squad Weapon (NGSW) program. The XM7 is chambered in a new 6.8x51mm cartridge designed to outperform the 5.56 NATO round at longer distances.

If you are building a preparedness kit around modern tactical equipment, you can choose your Crate Club tier to receive field-tested gear selected by professionals.

The M4A1 Carbine: The Current Standard

The M4A1 Carbine has been the primary individual weapon for the U.S. Army for decades. It is a shorter, lighter evolution of the original M16 rifle, optimized for modern combat where maneuverability in tight spaces—like vehicles or urban environments—is critical. The M4A1 is a gas-operated, air-cooled, magazine-fed, selective-fire weapon. Unlike the older M4, which featured a three-round burst setting, the M4A1 is "full auto" capable, allowing for a consistent trigger pull and better suppressive fire capabilities when necessary.

The M4A1 uses the 5.56x45mm NATO round, an intermediate cartridge designed for high velocity and low recoil. The rifle features a 14.5-inch barrel and a collapsible stock, making it highly adaptable to soldiers of different sizes and those wearing bulky body armor. Most Army M4s are equipped with the SOPMOD (Special Operations Peculiar MODification) kit, which includes a variety of accessories like the M68 Close Combat Optic (red dot), the ACOG (Advanced Combat Optical Gunsight), and various laser aiming devices like the PEQ-15.

For broader context on rifle platforms and their components, read this guide to what makes a tactical rifle.

The M4 platform relies on a Direct Impingement (DI) gas system. In this system, gas is tapped from the barrel and channeled through a tube directly back into the bolt carrier group to cycle the action. While this makes the rifle lightweight and accurate, it also introduces carbon fouling directly into the receiver, requiring diligent maintenance. For the average soldier, the M4A1 provides a reliable, accurate, and lightweight platform that has proven itself from the mountains of Afghanistan to the streets of Iraq.

The NGSW Program: Why the Army is Changing

The shift away from the M4A1 is driven by the evolution of modern warfare. The U.S. Army identified two primary concerns: the limited effective range of the 5.56mm round and the increasing prevalence of advanced body armor among "near-peer" adversaries. While the 5.56mm is lethal, its effectiveness drops off significantly past 300 meters, especially when fired from the shorter barrel of a carbine.

The Next Generation Squad Weapon (NGSW) program was launched to find a replacement that offered more "overmatch"—the ability to outrange and outgun the enemy. After a rigorous selection process, the Army chose SIG Sauer to produce both the rifle (XM7) and the automatic rifle (XM250), as well as the unique 6.8mm ammunition they fire.

Key Goals of the NGSW Program:

• Increased Lethality: The ability to defeat modern ceramic body armor plates at extended ranges.
• Greater Range: Extending the effective engagement distance beyond the 500-meter mark.
• Advanced Fire Control: Integrating high-tech optics that calculate ballistics in real-time.
• Standardized Suppression: Every XM7 is designed to be run with a suppressor to reduce the acoustic signature and muzzle flash.

Key Takeaway: The Army is moving from the M4 to the XM7 to gain a ballistic advantage over modern body armor and to increase the effective range of the individual infantryman.

The XM7: The Army’s New Assault Rifle

The XM7 (initially designated the XM5) is the rifle variant of the NGSW program. It is based on the SIG Sauer MCX platform, which is already in use by various special operations units worldwide. Unlike the M4, the XM7 uses a Short-Stroke Gas Piston system. In this design, the gas pushes a piston that strikes the bolt carrier, keeping the carbon fouling and heat out of the receiver. This generally leads to higher reliability in harsh conditions and less frequent cleaning requirements.

The XM7 features fully ambidextrous controls, a folding stock, and a full-length Picatinny rail for mounting optics and accessories. It is significantly heavier than the M4A1, weighing in at roughly 8.4 pounds (unloaded) compared to the M4’s 6.4 pounds. When you add the suppressor and the new high-tech optic, the weight difference becomes a major factor for the soldier on the ground.

The XM7's primary features include:

• Side-charging and Rear-charging handles: Gives the operator options for clearing malfunctions or loading.
• M-LOK Handguard: Allows for direct attachment of accessories without the bulk of traditional quad rails.
• Two-Stage Trigger: Provides a crisp break for better long-range accuracy.
• Quick-Suppressor Attachment: Designed specifically for the SIG SLX series of suppressors.

Readers comparing platforms can also browse tactical rifle essentials before evaluating supporting equipment.

The 6.8x51mm Common Cartridge

The most critical part of the new system isn't the rifle itself, but the ammunition. The 6.8x51mm Common Cartridge is a hybrid design. To handle the incredibly high pressures required to achieve its performance goals (up to 80,000 psi), the cartridge uses a stainless steel base joined to a brass body. This allows the round to be lighter than a traditional all-brass .308 Winchester round while being much more powerful.

This cartridge bridges the gap between the 5.56mm NATO and the 7.62x51mm NATO. It has a flatter trajectory and retains more energy at long range than either of its predecessors. For the tactical enthusiast, this means the Army is essentially moving back toward a "battle rifle" philosophy, prioritizing power and distance over the "carry more, shoot more" philosophy of the 5.56mm era.

Field Note: Transitioning to a heavier rifle and heavier ammunition means your physical conditioning and load carriage setup become even more important. If you are building a kit around a heavier platform like the XM7's civilian counterpart (the MCX Spear), ensure your plate carrier and belt setup can handle the added weight of the mags.

For load-bearing accessories, maintenance tools, and everyday-carry equipment, browse the Gear Shop.

The XM157 Fire Control System

A rifle is only as good as the soldier's ability to aim it. Along with the XM7, the Army is fielding the XM157 Next Generation Squad Weapon-Fire Control (NGSW-FC). Produced by Vortex Optics, this is not just a scope; it is a computer.

The XM157 is a 1-8x30 optic that integrates a laser rangefinder, a ballistic calculator, an atmospheric sensor suite, and an internal display. When a soldier looks through the optic and "lases" a target, the system instantly calculates the bullet's drop based on the distance, angle, and weather conditions. It then projects an "active reticle" or a corrected aiming point onto the lens. This technology effectively removes the guesswork of long-range shooting, allowing even an average marksman to make hits at 600 meters and beyond.

The optic also features wireless connectivity, allowing it to "talk" to other devices, such as enhanced night vision goggles. This allows a soldier to see the reticle and the target even if they are firing from behind cover without a traditional cheek weld. For those looking for this level of technology in their own kits, the Major tier often includes advanced optics and illumination tools that mirror this professional-grade evolution.

Comparing the Platforms: M4A1 vs. XM7

It is important to understand that the M4A1 will not disappear overnight. The Army plans to issue the XM7 primarily to "close combat forces"—infantry, cavalry scouts, and combat engineers. Support personnel and those in non-combat roles will likely carry the M4A1 for years to come.

The M4A1 wins on weight and portability. A soldier can carry significantly more 5.56mm ammunition for the same weight as the 6.8mm. However, the XM7 wins on lethality, barrier penetration, and range. In a scenario where an adversary is wearing high-level body armor or engaging from a distance, the XM7 is the superior tool.

To see how Crate Club approaches advanced optics and equipment, explore the Major What's Inside page.

Maintaining the Edge: Training and Gear

Whether you are using an M4-style AR-15 or a modern piston-driven rifle like the MCX, the fundamentals of maintenance remain the same. The Army's move to a piston system like the XM7 reduces the carbon in the receiver, but it increases the complexity of the front end of the rifle.

For a more detailed maintenance reference, review this assault rifle cleaning guide.

Basic Rifle Maintenance Steps:

Step 1: Clear the weapon. / Ensure the magazine is removed, the chamber is empty, and the safety is engaged. Step 2: Field strip the platform. / Remove the takedown pins and separate the upper and lower receivers. For the XM7, this also includes removing the piston assembly. Step 3: Clean the critical components. / Focus on the bolt carrier group, the chamber, and the gas system components. Use a high-quality CLP (Cleaner, Lubricant, and Preservative). Step 4: Inspect for wear. / Check the gas rings (on DI guns), the firing pin, and the extractor for any signs of fatigue or damage. Step 5: Lubricate and reassemble. / Apply lubricant to the friction points of the bolt carrier and the charging handle before putting the rifle back together.

At Crate Club, we emphasize that having the rifle is only half the battle. You need the cleaning kits, the tools, and the medical supplies to support yourself in the field. Our Captain tier is a popular choice for those building out their support gear, as it frequently includes the high-quality tools and everyday carry (EDC) essentials needed to keep your equipment running.

You can also shop maintenance and tactical equipment to build out a practical support kit.

The Civilian Version: SIG Sauer MCX Spear

For those in the civilian world, the Army’s choice of the XM7 has already had a major impact. SIG Sauer released the MCX Spear, which is the civilian-legal, semi-automatic version of the XM7. It is available in the same 6.8x51mm (marketed as .277 SIG Fury) as well as more common calibers like 7.62x51mm NATO (.308 Win) and 6.5 Creedmoor.

Owning a civilian version of the Army’s newest rifle allows enthusiasts to train with the same ergonomics and manual of arms as the modern soldier. However, the .277 SIG Fury ammunition is currently expensive and difficult to find compared to 5.56mm or .308. For most preppers, the M4-style AR-15 remains the most practical choice due to the sheer availability of parts and ammunition.

Field Note: If you choose to adopt the newer 6.8mm platform, your logistics chain becomes your weakest link. Standardize your gear but keep a 5.56mm or .308 backup to ensure you can find ammo in a long-term SHTF (Stuff Hits The Fan) scenario.

The Future of Army Small Arms

The transition to the XM7 is just the beginning. The Army is also integrating the XM250, the lightweight belt-fed machine gun meant to replace the M249 SAW (Squad Automatic Weapon). Like the XM7, the XM250 is chambered in 6.8mm and is significantly lighter than the weapon it replaces.

This holistic change to the squad's firepower signifies a move toward precision and distance. The Army is no longer content with "area fire"; they want "point lethality" at distances previously reserved for snipers. This shift will likely influence law enforcement agencies and civilian manufacturers for the next twenty years.

For the serious tactician, staying ahead of these trends is vital. Whether you are an active-duty soldier preparing for the new issue or a civilian prepper refining your loadout, understanding the capabilities of the XM7 helps you make better gear decisions. We see this evolution every day in the equipment we curate for our members. From the survival tools in our Lieutenant tier to the professional-grade tactical equipment in our General tier, we ensure our community has the gear that professionals trust.

Bottom line: The Army is currently transitioning from the 5.56mm M4A1 Carbine to the 6.8mm XM7 Rifle to achieve greater range and lethality against modern threats.

Conclusion

The U.S. Army's move to the XM7 and the 6.8mm cartridge marks the end of the 5.56mm's absolute dominance. While the M4A1 remains an iconic and highly effective tool, the XM7 represents the next leap in combat technology. It brings a sophisticated fire control system, a more powerful cartridge, and a more reliable operating system to the front lines.

Staying prepared means understanding these shifts and adapting your own training and gear accordingly. At Crate Club, our mission is to provide you with the same high-value, field-tested gear that operators rely on. Our crates are hand-picked by Spec Ops veterans who know exactly what it takes to perform when it counts. Whether you are just starting your journey or looking for front-line caliber equipment, we have a tier designed for your mission.

Explore Crate Club subscription tiers today and start building a kit that is ready for the future of the tactical landscape.

FAQ

What is the difference between the M4 and the XM7?

The M4 is a 5.56mm carbine using a direct impingement gas system, while the XM7 is a 6.8mm rifle using a short-stroke gas piston system. The XM7 is heavier but offers significantly more range, lethality, and a more advanced integrated optic system.

Can civilians buy the Army’s new rifle?

Yes, SIG Sauer produces a civilian version of the XM7 called the MCX Spear. It is a semi-automatic rifle available in .277 SIG Fury (the civilian equivalent of 6.8x51mm), as well as .308 Winchester and 6.5 Creedmoor.

Why did the Army choose 6.8mm over 5.56mm?

The 6.8mm round was chosen because it provides better penetration against modern body armor and maintains higher kinetic energy at longer ranges. The 5.56mm round was found to be less effective in the long-range engagements common in modern mountainous or open-terrain combat.

What is the XM157 optic?

The XM157 is the Army's new "smart" optic for the XM7, featuring a 1-8x magnification range, an onboard ballistic computer, and a laser rangefinder. It automatically calculates the bullet's point of impact and displays a corrected aiming point to the soldier in real-time.