The 350 Legend is a straight walled centerfire rifle cartridge featuring a standard maximum bullet diameter of 0.357 inches (9.07 mm). The maximum case length is 1.710 inches (43.43 mm), and the maximum overall cartridge length is restricted to 2.260 inches (57.40 mm) to ensure compatibility with standard AR-15 magazine wells.The case utilizes a rebated rim diameter of 0.378 inches (9.60 mm) and tapers slightly from a wider base diameter of 0.390 inches (9.91 mm) to a case mouth diameter of 0.378 inches.Ammunition for this caliber is most commonly found in 145 grain, 150 grain, 160 grain, 170 grain, and 180 grain bullet weights, with heavy 250 grain or 265 grain subsonic options also available. Exact dimensions can vary slightly depending on manufacturing tolerances and allowable specifications.
350 Legend Dimensions
| Dimension | Specification | Source | Notes |
| Bullet Diameter | 0.357 in (9.07 mm) | SAAMI | Maximum size; many manufacturers utilize 0.355 in projectiles. |
| Case Length | 1.710 in (43.43 mm) | SAAMI | Maximum case length; trim to length is typically 1.700 in. |
| Overall Cartridge Length | 2.260 in (57.40 mm) | SAAMI | Maximum overall length for standard AR-15 style magazines. |
| Rim Diameter | 0.378 in (9.60 mm) | SAAMI | Reuses the standard 223 Remington bolt face dimension. |
| Case Diameter (Base) | 0.390 in (9.91 mm) | SAAMI | Measured just above the extractor groove. |
| Shoulder Diameter | N/A | N/A | Straight walled cartridge; no shoulder. |
| Neck Diameter | 0.378 in (9.60 mm) | SAAMI | Maximum external diameter at the case mouth. |
| Base Diameter | 0.390 in (9.91 mm) | SAAMI | Wider than the rim, making it a rebated rim cartridge. |
| Case Capacity | 36.5 gr H2O | Industry | Varies slightly based on the brass manufacturer. |
| Maximum Pressure | 55,000 psi | SAAMI | Governed by SAAMI specifications for modern bolt actions and AR-15s. |
Understanding The 350 Legend Dimensions
- Bullet Diameter: The measurement across the widest point of the bullet. For the 350 Legend, this is specified as a maximum of 0.357 inches. This dimension ensures the projectile seals properly within the barrel rifling to trap expanding gases and generate velocity.
- Case Length: The length of the empty brass cylinder from the base to the case mouth, maxing out at 1.710 inches. This specific length allows the cartridge to be used for hunting in states that mandate straight walled cartridges between 1.160 and 1.800 inches.
- Overall Cartridge Length (OAL): The total length of the fully assembled round from the base to the tip of the bullet, strictly capped at 2.260 inches. OAL directly influences whether a cartridge will fit into a standard magazine and feed properly through the firearm action.
- Rim Diameter: The diameter of the flange at the very bottom of the case (0.378 inches). The firearm extractor hooks onto this rim to pull the spent casing out of the chamber. Because it matches the 223 Remington, the 350 Legend uses a standard AR-15 bolt.
- Case Diameter: The width of the cartridge body at the base. At 0.390 inches, it is wider than the rim, forming what is known as a rebated rim.
- Case Capacity: Measured in grains of water (gr H2O), this represents the internal volume of the empty case. Averaging 36.5 grains of water, it dictates how much gunpowder the case can safely hold.
- Maximum Pressure: The peak internal pressure generated when the cartridge is fired. Standard SAAMI limits set this at 55,000 psi to ensure the firearm does not suffer catastrophic failure.
350 Legend Cartridge Dimensions In Inches And Millimeters
For engineers, reloaders, and international shooters, below are the primary 350 Legend measurements converted accurately between imperial and metric systems.
| Dimension | Inches (SAAMI Max) | Millimeters (Equivalent) |
| Bullet Diameter | 0.357 in | 9.07 mm |
| Case Length | 1.710 in | 43.43 mm |
| Overall Length | 2.260 in | 57.40 mm |
| Rim Diameter | 0.378 in | 9.60 mm |
| Base Diameter | 0.390 in | 9.91 mm |
| Neck Diameter | 0.378 in | 9.60 mm |
350 Legend Case Dimensions
The 350 Legend is defined by a rimless, straight walled case featuring a rebated rim. The official maximum case length is 1.710 inches (43.43 mm), with a nominal trim to length for reloaders sitting at 1.700 inches.The base diameter measures 0.390 inches, while the rim diameter is cut narrower at 0.378 inches.
Because the case is essentially straight walled with a very slight body taper, it offers a large internal volume for its compact size. The internal case capacity is roughly 36.5 grains of water. This capacity is highly efficient, allowing the 350 Legend to push 0.357 caliber bullets at high hunting velocities using relatively small charges of fast burning rifle powders.
350 Legend Bullet Diameter
The standardized maximum bullet diameter for the 350 Legend is 0.357 inches (9.07 mm). However, this specific measurement is a frequent source of confusion among shooters and reloaders.
SAAMI lists the bullet diameter with a negative tolerance, meaning the projectile can technically measure anywhere from 0.354 to 0.357 inches and still be within specification. In practice, ammunition manufacturers often load the 350 Legend with 0.355 inch projectiles, which is the exact same standard width used for 9mm Luger pistol bullets.
The standard 350 Legend barrel features a groove diameter of 0.355 inches and a bore or land diameter of 0.346 inches. Firing a 0.355 or 0.357 inch bullet down a 0.355 inch groove diameter forces the copper jacket to engrave tightly into the rifling, creating the necessary spin to stabilize the projectile accurately in flight.
350 Legend Overall Length
The SAAMI maximum overall cartridge length (OAL) for the 350 Legend is 2.260 inches (57.40 mm). This number is a hard limit designed to guarantee that the cartridge will fit perfectly inside standard AR-15 magazines without modifying the lower receiver of the firearm.
Typical factory cartridge length varies drastically based on the bullet profile. A 145 grain full metal jacket or 150 grain hunting bullet often measures close to the maximum 2.260 inches. In contrast, heavy 250 grain or 265 grain subsonic bullets are exceptionally long. To maintain the 2.260 inch overall length restriction, these massive bullets must be seated very deeply into the brass case, which significantly reduces the available powder capacity and requires specific subsonic reloading data.
350 Legend Chamber And Cartridge Dimensions
The relationship between the 350 Legend cartridge and the firearm chamber is critical for reliable functionality. Because it lacks a bottleneck shoulder, the 350 Legend cartridge headspaces on the case mouth.
This means the flat forward edge of the brass casing physically stops against a machined ledge inside the barrel chamber. Proper case length is absolutely mandatory. If the brass stretches beyond 1.710 inches, the cartridge will pinch in the chamber throat, which can prevent the bolt from closing or cause dangerous pressure spikes upon firing. Additionally, because the cartridge headspaces on the case mouth, reloaders must apply a taper crimp rather than a heavy roll crimp. A roll crimp would fold the brass inward, removing the sharp edge the cartridge needs to stop securely in the chamber.
350 Legend Dimensions vs Similar Cartridges
To understand the 350 Legend size profile, it is helpful to compare it against other popular intermediate rifle cartridges.
| Cartridge | Bullet Diameter | Case Length | Overall Length | Base Diameter | Maximum Pressure | Source |
| 350 Legend | 0.357 in | 1.710 in | 2.260 in | 0.390 in | 55,000 psi | SAAMI |
| 223 Remington | 0.224 in | 1.760 in | 2.260 in | 0.376 in | 55,000 psi | SAAMI |
| 300 Blackout | 0.308 in | 1.368 in | 2.260 in | 0.376 in | 55,000 psi | SAAMI |
| 360 Buckhammer | 0.358 in | 1.800 in | 2.500 in | 0.419 in | 50,000 psi | SAAMI |
| 450 Bushmaster | 0.452 in | 1.700 in | 2.260 in | 0.500 in | 38,500 psi | SAAMI |
350 Legend vs 223 Remington Dimensions
The 350 Legend is heavily tied to the 223 Remington because both cartridges are optimized for the AR-15 platform. However, their physical dimensions are critically different.
- Shared Dimensions: Both cartridges share an identical 0.378 inch rim diameter. Both are strictly restricted to a 2.260 inch maximum overall length to fit AR-15 magazines. Because of the shared rim size, a 350 Legend rifle utilizes a standard 5.56 NATO or 223 Remington bolt carrier group.
- Dimensional Differences:The 350 Legend case is shorter (1.710 inches vs 1.760 inches) and has a noticeably wider base.The 350 Legend base measures 0.390 inches, whereas the 223 Remington measures 0.376 inches.
- Lack of Interchangeability: Because of this wider base dimension, the 350 Legend is not simply a necked up 223 Remington case. You cannot physically form safe 350 Legend brass by blowing out 223 Remington cases. The wider, straight walled body of the 350 Legend also requires dedicated magazines to feed reliably.
350 Legend SAAMI vs C.I.P. Dimensions
Cartridge dimensions and safe pressure limits are strictly governed by SAAMI in the United States. Winchester designed the cartridge and submitted it to SAAMI, which standardized the 350 Legend in 2019.
SAAMI lists the maximum average pressure for the 350 Legend at 55,000 psi, measured via conformal piezoelectric transducers. C.I.P. in Europe does not always immediately adopt highly specialized American hunting cartridges, but any ammunition manufactured to SAAMI specifications is considered safe and standard globally.
350 Legend Bullet Weight And Dimensions
The 350 Legend is loaded heavily in two completely different bullet weight categories that change how the internal dimensions of the cartridge are configured.
- Supersonic (145 to 180 grain): These shorter, lighter bullets fly significantly faster than the speed of sound. They do not require extreme seating depths, leaving maximum case capacity for the gunpowder required to push them to high velocities for deer hunting.
- Subsonic (250 to 265 grain): These massive, long bullets are designed to stay below the speed of sound, making them exceptionally quiet when fired through a suppressor. To maintain the 2.260 inch overall length restriction, these long bullets must be seated very deeply into the brass case, which significantly reduces the available powder capacity.
Bullet weight does not alter the external brass case dimensions, but the manufacturer must carefully manage bullet seating depth to ensure safe chamber pressures.
Why 350 Legend Dimensions Matter
Understanding the specific 350 Legend measurements is essential for several practical reasons.
- Hunting Regulations: The 1.710 inch case length was specifically chosen because many states restrict straight walled hunting cartridges to a maximum case length of 1.800 inches. The 350 Legend fits comfortably within this legal definition.
- Parts Compatibility: Knowing that the rim diameter (0.378 inches) matches the 223 Remington allows shooters to build a 350 Legend AR-15 using standard bolt carrier groups and lower receivers. Only the barrel and the magazines need to be changed.
- Reloading Safety: Because the cartridge headspaces on the case mouth, reloaders must meticulously measure their brass. Cases trimmed too short will suffer light primer strikes, and cases left too long will jam in the chamber.
Manufacturer Specifications vs Independent Measurements
If you use calipers to measure factory 350 Legend ammunition from companies like Winchester or Hornady, the numbers will rarely match the SAAMI maximum specifications exactly.
SAAMI publishes maximum allowable dimensions to ensure absolute safety and interoperability. Ammunition manufacturers purposefully produce their cases slightly smaller than these maximums. For example, the maximum case length is 1.710 inches, but measuring a factory cartridge might reveal a case length of 1.702 inches. This built in negative tolerance margin guarantees that the ammunition will chamber reliably in the field, even if the rifle is fouled from carbon buildup.
Common Questions
What are the dimensions of the 350 Legend?
The key maximum dimensions are a bullet diameter of 0.357 inches, a case length of 1.710 inches, and an overall cartridge length of 2.260 inches.
What is the 350 Legend case length?
The maximum SAAMI case length is 1.710 inches (43.43 mm).
What is the 350 Legend overall length?
The maximum overall length (OAL) is 2.260 inches (57.40 mm), designed to fit standard AR-15 magazines.
What is the 350 Legend bullet diameter?
The SAAMI maximum bullet diameter is 0.357 inches, but many manufacturers use 0.355 inch projectiles.
What is the 350 Legend rim diameter?
The rim diameter measures 0.378 inches, identical to the 223 Remington.
What is the 350 Legend case diameter?
The case diameter at the base is 0.390 inches, tapering slightly to 0.378 inches at the case mouth.
What is the 350 Legend case capacity?
The 350 Legend holds approximately 36.5 grains of water, depending on the thickness of the specific brass casing.
What is the maximum pressure for the 350 Legend?
The SAAMI maximum average pressure is strictly capped at 55,000 psi.
How do 350 Legend and 223 Remington dimensions compare?
They share the same rim diameter (0.378 in) and maximum overall length (2.260 in), but the 350 Legend uses a shorter case (1.710 in), a wider base (0.390 in), and a much larger 0.357 inch bullet.
Does the 350 Legend use the same bolt as a 223 Remington?
Yes. Because they share the exact same 0.378 inch rim diameter, the 350 Legend uses a standard 223 Remington bolt carrier group.