350 Legend Upper: A Complete Guide

350 Legend Upper: A Complete Guide

The 350 Legend Upper is a popular choice for hunters and shooting enthusiasts looking for a reliable and accurate rifle on the AR-15 Platform. This upper is designed to fit onto a standard AR-15 lower and provides a powerful and versatile option for medium-sized game hunting. The 350 Legend cartridge was introduced by Winchester in 2019, primarily to address requirements in several states that deer be hunted with centerfire, straight-walled cartridges. The .350 Legend has quickly gained popularity among hunters and shooters alike.

Understanding the .350 Legend Upper for the AR-15 platform is crucial for anyone looking to purchase one. The technical specifications of the 350 Legend barrel are important to consider, as they will affect accuracy and performance. Complete 350 Legend uppers and their components are also important to understand, as they will contribute to overall performance and reliability. Finally, well matched optics and proper magazines for the 350 Legend complete upper can enhance the shooting and hunting experiences.

Key Takeaways

  • The 350 Legend Upper for AR-15 is a popular choice for hunters and shooting enthusiasts.
  • A high quality barrel is essential to the accuracy, performance, and reliability of the 350 Legend upper.
  • Optics, magazines, and other components are also essential considerations when choosing a 350 Legend complete upper for your AR-15 rifle.

The 350 Legend Cartridge

The 350 Legend ammunition is a straightwall centerfire cartridge that was introduced by Winchester in 2019. It has a bullet diameter of .357 - 0.0030 inches, a shell case length of 1.71 inches, and an overall cartridge length of 2.26 inches. Depending on bullet mass, muzzle velocities range from subsonic to 2,350 ft/sec, making it the fastest SAAMI-approved, straight-walled cartridge for the AR-15 platform. It is designed to offer greater penetration, kinetic energy, and terminal performance than other AR-15 ammunition including .223 Remington and 300 Blackout, while remaining low recoil.

The 350 Legend case offers similarities to the .223 Remington, including rim diameter (0.378 inches), however it is not derived from the .223 Remington. As a result, the standard 223/5.56 BCG is compatible with 350 Legend as well.

350 Legend factory bullet weights range from 145 gr (2350 ft/sec) to 255 gr (1060 ft/sec). The most common bullet weights are between 150 gr (2325 ft/sec) and 180 gr (2100 ft/set). Winchester asserts that the 350 Legend is effective to 250 yards with flatter trajectory and lower recoil that other commercially available straight-walled centerfire cartridges.

Technical Specifications of 350 Legend Barrel

Barrel Length

The standard barrel length for a 350 Legend AR-15 upper assembly is between 16 and 20 inches. While it is true that longer barrels produce higher muzzle velocities, data shows that there is a 100 ft/sec difference for 350 legend between 16 inches and 24 inches. A 350 Legend Upper with a quality barrel between 16 and 18 inches will deliver sub MOA performance with factory ammunition. The advantages gained from a 20 inch barrel, or longer, are negligible. Therefore, the weight-to-performance sweet spot for 350 Legend is the 16 and 18 inch barrel options.

Gas System

350 Legend barrels are typically delivered with Carbine Length gas systems on the AR-15 platform.

Twist Rate

Winchester designed the 350 Legend for a 1:16 twist rate. This twist rate is optimized for the 180-grain bullets and 16 inch barrels, however the 1:16 twist rate works very well for other bullet weights and barrel lengths as well.

Feed Ramp

The feed ramp for a 350 Legend upper can be either M4 or 30 Cal. While M4 feed ramps are more common, feed reliability is improved with 30 Cal feed ramps. It is straightforward to modify M4 feed ramps to the 30 Cal profile.

Barrel Material

The most common barrel material for 350 Legend is chrome-moly steel or chrome-moly-vanadium (CMV) steel. There is not significant difference between chrome-moly steel barrels and chrome vanadium steel barrels. Both types are durable, heat-resistant, and provide excellent accuracy and longevity. Chrome-moly barrel finishes include parkerized or nitrided.

350 Legend stainless steel barrels are also offered, and are very popular. Stainless barrels are higher rigidity and less prone to heating, yielding better accuracy, especially across multiple shots.

Bolt Carrier Group (BCG)

The bolt carrier group (BCG) for a 350 Legend upper is the same 233/5.56 BCG used in a standard AR-15. This is a significant cost advantage for 350 Legend over other calibers that require a specialized BCG.

Complete 350 Legend Uppers and Their Components

When it comes to building an AR-15 chambered in .350 Legend, purchasing a complete upper is a convenient and cost-effective option. Complete uppers come with all the necessary components to attach to a lower receiver and start shooting. Here are the components you can expect to find in a complete 350 Legend upper.


The barrel is the most important component of an upper assembly and can greatly affect the accuracy and performance of the rifle. A 350 Legend barrel typically has a length of 16 to 20 inches and a twist rate of 1:16. The barrel can be made from different materials such as chrome-moly steel, stainless steel, or carbon fiber. The choice of material can affect the weight, durability, and heat dissipation of the barrel.

Upper Receiver

The upper receiver is the part of the upper assembly that attaches to the lower receiver and houses the bolt carrier group and charging handle. A 350 Legend upper receiver can be made from aluminum or polymer and can have different coatings such as anodized or Cerakote. The highest reliability upper receivers are made from 7075 Aluminum forgings that are precision machined to the mil-spec designs. The mil-spec upper receiver will have a forward assist and dust cover, and there are side charging options as well.

Muzzle Brake / Flash Hider

The muzzle brake or flash hider is threaded to the end of the barrel and can reduce recoil and muzzle rise or suppress flash and noise. A 350 Legend muzzle device can be a brake, compensator, flash hider, or suppressor. The choice of muzzle device can depend on the intended use of the rifle such as hunting, competition, or tactical. There is also a suppressed option for 350 Legend enthusiasts.


The handguard is the part of the upper assembly that surrounds the barrel and provides a place to mount accessories such as optics, lights, and grips. A 350 Legend handguard can be made from different materials such as aluminum or polymer and can have different lengths and styles. The handguard can also have different features such as a free-floating design or a Picatinny rail system, and also M-LOK or Keymod attachment points.

Bolt Carrier Group

The bolt carrier group is the workhorse of the upper assembly and is responsible for loading, firing, and ejecting the cartridge. A 350 Legend bolt carrier group can be made from different materials such as steel or titanium and can have different coatings such as Nitride or Nickel Boron. The most important thing to remember about the 350 Legend Bolt Carrier Group is that it is the same as the standard 223/556 Bolt Carrier Group.

Charging Handle

The charging handle is the part of the upper assembly that is used to manually chamber the first round by pulling back the bolt carrier group. A 350 Legend charging handle can be made from aluminum or steel and can have different sizes and shapes. The charging handle can also have different features such as an extended latch or ambidextrous design.

In conclusion, a complete 350 Legend upper can be a great option for those who want to quickly and easily build an AR-15 chambered in this powerful cartridge. By understanding the components of a complete upper, you can make an informed decision on which one to purchase based on your needs and preferences.

350 Legend Upper for Hunting

AR-15s are popular firearms for hunting medium-sized game, and the 350 Legend upper is a great addition to any hunting rifle collection. The 350 Legend cartridge is a straight-walled cartridge that is perfect for hunting deer, hogs, and other medium game.

Deer Hunting

The 350 Legend cartridge is a great choice for deer hunters, and in fact, was designed specifically with deer hunting in mind. With its flat trajectory and excellent accuracy, it is perfect for taking down deer out to 200 yards. The cartridge is also known for its low recoil, making it easier to shoot accurately. Hunters can use a 350 Legend upper with a mil-spec AR-15 to create a lightweight and versatile deer hunting rifle. 350 Legend is one of a limited number of options available to deer hunters in states that require straight-walled centerfire cartridges.

Hog Hunting

Hog hunting can be challenging, but the 350 Legend cartridge is up to the task. The cartridge's high penetration and energy make it ideal for taking down hogs. Hog hunters can use a 350 Legend upper with a heavy barrel to increase accuracy and reduce recoil.

Overall, the 350 Legend upper is an excellent addition to any hunting rifle collection. Whether you are hunting deer, hogs, or other medium game, the 350 Legend cartridge has the accuracy, velocity, energy, and terminal performance you need to take down your prey.

Optics and Magazines for 350 Legend Uppers

When it comes to hunting with a 350 Legend Upper, having the right optics and magazines can make all the difference. This section will cover some of the essential accessories that can help improve your accuracy and overall hunting experience.


A high-quality scope is essential for any hunting rifle, and the 350 Legend Upper is no exception. A scope with a magnification of at least 4x is recommended for medium-range hunting. A magnification range of 1-6 or 1-8 is ideal out to the 250 yard effective range of the 350 Legend round.

350 Legend Magazine

Magazines are the one place where 350 Legend is not compatible with 223/5.56 components. There are claims that 350 Legend ammunition will feed from 223/5.56 magazines, but don't be fooled - it is at best unreliable. Choose a high-quality, purpose-built 350 Legend Magazine and skip the frustration.

The 350 Legend Upper requires a specific magazine that is designed to accommodate the straight-walled cartridge. It is essential to use a magazine that is designed for the 350 Legend to ensure reliable feeding and prevent malfunctions. For the 350 Legend, both polymer and steel magazines are available in various capacities. The recommended magazine capacity options range from 5 to 20 rounds, depending on your specific needs and preferences.

Purchasing a 350 Legend Upper

When purchasing a 350 Legend upper for an AR-15, it is important to consider a few key factors to ensure a high-quality and reliable product.

First and foremost, the barrel is one of the most important components of the upper. A high-quality barrel will not only improve accuracy, but also ensure longevity and durability. Look for barrels made from high-grade materials, such as chrome-moly or stainless steel, with a carbine length gas system and 1:16 twist rate to optimize performance with the 350 Legend cartridge. The weight-performance sweet spot is the 16 and 18 inch barrel options.

In addition, the upper receiver should be forged for maximum strength and durability. This will ensure that the upper can withstand the recoil and stress of firing the 350 Legend cartridge.

A lightweight hand guard can also be beneficial, as it will reduce overall weight and improve maneuverability. Look for hand guards made from durable materials such as aluminum or polymer, with a slim profile to reduce bulk.

When purchasing a 350 Legend upper, it is also important to use purpose built 350 Legend magazines in either polymer or steel. A dedicated 350 Legend magazine will improve feeding reliability and ensure proper function of the upper.

Finally, don't forget to include a scope when purchasing a 350 Legend upper. A scope will improve accuracy and allow for better target acquisition, making the 350 Legend cartridge even more effective for hunting and shooting applications.

Overall, when purchasing a 350 Legend upper, it is important to consider all of these factors to ensure a high-quality and reliable product that will provide optimal performance with the 350 Legend cartridge.