The 400 Legend is a standardized straight-walled centerfire rifle cartridge featuring a maximum case length of 1.650 inches (41.91 mm) and an overall cartridge length of 2.260 inches (57.40 mm).Based on official SAAMI specifications accepted in 2023, the rebated rim case features a 0.422 inch rim diameter, a 0.440 inch base diameter, and a 0.4267 inch neck diameter. As a straight-walled cartridge, it possesses no shoulder and headspaces directly on the case mouth. Published specifications represent maximum material conditions, though physical measurements may vary slightly based on manufacturing tolerances.
400 Legend Case Dimensions
| Case Dimension | Inches | Millimeters | Specification Type | Source | Notes |
| Case Length | 1.650 | 41.91 | Maximum | SAAMI | Standard trim to length is 1.640 in. |
| Rim Diameter | 0.422 | 10.72 | Maximum | SAAMI | Matches the 6.8 SPC bolt face. |
| Rim Thickness | 0.049 | 1.24 | Maximum | SAAMI | Controls extractor engagement. |
| Base Diameter | 0.440 | 11.18 | Maximum | SAAMI | Measured just above the extractor groove. |
| Shoulder Diameter | N/A | N/A | N/A | SAAMI | Straight-walled case. |
| Neck Diameter | 0.4267 | 10.84 | Maximum | SAAMI | Outside case neck diameter. |
| Neck Length | N/A | N/A | N/A | SAAMI | Straight-walled case. |
| Shoulder Angle | N/A | N/A | N/A | SAAMI | Straight-walled case. |
| Overall Length | 2.260 | 57.40 | Maximum | SAAMI | Fits standard AR-15 magazines. |
| Case Capacity | ~44.0 | 2.85 cm³ | Nominal (H2O) | Industry Std. | Varies by brass manufacturer. |
| Maximum Pressure | 45,000 | 310.26 MPa | Max Average | SAAMI (Piezo) | Optimized for straight-walled deer regulations. |
Understanding The 400 Legend Case Dimensions
To understand how the 400 Legend interacts with a rifle chamber, bolt, and magazine, you must analyze its discrete geometric components. Because it is classified as a straight-walled cartridge, its geometry serves a different engineering purpose than bottleneck rifle cases.
- Case Length: Measured from the base of the rim to the case mouth. This dimension dictates the space available for powder and determines exactly where the cartridge headspaces inside the chamber.
- Rim Diameter and Thickness: The rim provides the gripping surface for the rifle extractor. The 400 Legend utilizes a rebated rim, meaning the rim is narrower than the main case body to fit a specific standard bolt face.
- Base Diameter: This is the width of the main cartridge body just ahead of the extractor groove. The unusually wide base gives the 400 Legend its power advantage without requiring a long case.
- Shoulder Diameter and Geometry: The 400 Legend does not have a shoulder.
- Neck Diameter and Length: Without a shoulder step, the case maintains a slight taper from the 0.440 inch base directly to the 0.4267 inch case mouth.
- Overall Cartridge Length (OAL): The measurement from the case base to the tip of the seated bullet. This 2.260 inch maximum length dictates that the cartridge will fit perfectly inside standard AR-15 platform magazines.
- Case Capacity: The internal volume of the case, generally expressed in grains of water (gr H2O). This dictates the maximum powder charge the cartridge can safely hold.
400 Legend Case Dimensions In Inches And Millimeters
Official SAAMI standardization utilizes inches, but metric parameters are frequently referenced by international shooters and brass manufacturers.
| Dimension | Measurement (Inches) | Measurement (Millimeters) |
| Maximum Case Length | 1.650 in | 41.91 mm |
| Maximum Rim Diameter | 0.422 in | 10.72 mm |
| Maximum Base Diameter | 0.440 in | 11.18 mm |
| Maximum Neck Diameter | 0.4267 in | 10.84 mm |
| Maximum Overall Length | 2.260 in | 57.40 mm |
400 Legend Case Length
The published maximum case length for the 400 Legend is 1.650 inches (41.91 mm). This specific dimension was chosen deliberately by Winchester engineers. Many American states strictly mandate a maximum case length of 1.800 inches for straight-walled deer hunting cartridges on public lands.
By keeping the case at 1.650 inches, the 400 Legend remains fully compliant with these public land hunting regulations while leaving enough physical room within the 2.260 inch overall length to seat heavy, aerodynamic 400 caliber projectiles. Because straight-walled cases headspace on the case mouth, consistent case length is highly critical. Most reloaders use a trim length of 1.640 inches to ensure a uniform crimp and safe headspace on every round.
400 Legend Base And Rim Dimensions
The 400 Legend features a rebated rim design. The base diameter of the main case body measures 0.440 inches, but the rim diameter is reduced to 0.422 inches.
This 0.422 inch rim is a well established industry standard, sharing the exact same bolt face dimensions as the 6.8 SPC and the .224 Valkyrie. The rebated design allows the cartridge to pack more powder into a fatter 0.440 inch body while still reliably cycling through modern sporting rifles equipped with a standard 6.8 SPC bolt assembly.
400 Legend Shoulder And Neck Dimensions
Unlike traditional bottleneck rifle cartridges, the 400 Legend is classified as a straight-walled cartridge. It possesses no shoulder diameter, no shoulder angle, and no distinct neck length.
The brass simply extends forward from the 0.440 inch base to a maximum neck diameter of 0.4267 inches at the case mouth. This slight body taper of 0.0133 inches from the base to the mouth exists solely to prevent the brass from swelling and sticking to the chamber walls during the violent extraction process of a semi-automatic rifle. The neck holds a 0.4005 inch diameter bullet.
400 Legend Case Capacity
Case capacity heavily influences powder selection, velocity potential, and safe operating pressures. The nominal water capacity of the 400 Legend is approximately 44.0 grains of H2O.
However, this is not a static universal number. Actual internal volume fluctuates based on which manufacturer produces the brass. Thicker brass webbing near the case head will reduce internal volume. A reduction in case capacity causes standard powder charges to produce higher pressures, which is why load data must be adjusted when switching between different brands of 400 Legend brass.
400 Legend Case Dimensions vs 350 Legend
The 400 Legend was designed to offer significantly more energy than its older sibling, the 350 Legend.
| Dimension | 400 Legend | 350 Legend | Source |
| Case Length | 1.650 in | 1.710 in | SAAMI |
| Rim Diameter | 0.422 in (Rebated) | 0.378 in (Rebated) | SAAMI |
| Base Diameter | 0.440 in | 0.390 in | SAAMI |
| Bullet Diameter | 0.4005 in | 0.357 in | SAAMI |
| Overall Length | 2.260 in | 2.250 in | SAAMI |
| Case Capacity | ~44.0 gr H2O | ~36.5 gr H2O | Standard Data |
While both cartridges fit into an AR-15 magazine, they accomplish it differently. The 350 Legend uses a narrower 0.390 inch base and a longer 1.710 inch case. The 400 Legend utilizes a much fatter 0.440 inch base to increase powder capacity, necessitating a slightly shorter 1.650 inch case length to ensure the massive .400 caliber bullets fit within the magazine restrictions.
400 Legend Case Dimensions vs Similar Cartridges
The 400 Legend bridges the gap between medium bore and big bore straight-walled hunting cartridges.
| Cartridge | Case Length | Base Diameter | Rim Diameter | Bullet Diameter | Overall Length |
| 400 Legend | 1.650 in | 0.440 in | 0.422 in | 0.4005 in | 2.260 in |
| 350 Legend | 1.710 in | 0.390 in | 0.378 in | 0.357 in | 2.250 in |
| 450 Bushmaster | 1.700 in | 0.500 in | 0.473 in | 0.452 in | 2.260 in |
| 360 Buckhammer | 2.160 in | 0.419 in | 0.506 in | 0.358 in | 2.500 in |
400 Legend vs 450 Bushmaster Case Dimensions
The 450 Bushmaster is the heavy hitting competitor in the straight-walled AR-15 market.
- Similarities: Both the 400 Legend and 450 Bushmaster utilize rebated rims and share a maximum overall length of 2.260 inches to fit standard magazines.
- Differences: The 450 Bushmaster is significantly wider, featuring a 0.500 inch base diameter and requiring a standard 0.473 inch (.308 Winchester style) bolt face. The 400 Legend is narrower with a 0.440 inch base and uses a 6.8 SPC bolt face. Because the 400 Legend is slimmer, rifles can often stack more rounds in a magazine compared to the bulky 450 Bushmaster.
400 Legend Chamber And Case Dimensions
A rifle chamber must be fractionally larger than the cartridge it accepts. The relationship between 400 Legend case dimensions and chamber dimensions centers entirely on the case mouth.
Because there is no shoulder, headspace for the 400 Legend is measured from the bolt face to the lip of the chamber throat. The mouth of the brass case physically impacts this lip to stop the cartridge from sliding too far forward. If a case is trimmed too short, the firing pin may push the cartridge forward instead of detonating the primer. If the case is left too long, the bolt will fail to close.
400 Legend Case Forming And Resizing
A common misconception is that handloaders can form 400 Legend brass from 6.8 SPC brass because they share the same rim diameter. This is physically impossible.
The 6.8 SPC has a base diameter of 0.422 inches. The 400 Legend has a much wider base diameter of 0.440 inches. A reloader cannot safely stretch the solid brass web of a case head outward by 0.018 inches. Therefore, 400 Legend brass is proprietary and must be purchased as dedicated components. When reloading, the straight-walled case requires an expanding die to slightly “bell” the case mouth before seating the bullet, much like reloading a pistol cartridge.
400 Legend Manufacturer Specifications vs Actual Measurements
There is a documented difference between absolute standards and the dimensions of a physical cartridge sitting on a reloading bench.
SAAMI lists maximum material conditions. Ammunition manufacturers intentionally produce brass slightly smaller than these maximums to guarantee their cartridges will extract cleanly from dirty or tightly machined chambers. A fired 400 Legend case expands to the exact dimensions of the specific rifle chamber it was fired in. When a handloader runs this fired brass through a carbide sizing die, the machine compresses the base and body back down to factory nominal tolerances.
Common Questions
What are the 400 Legend case dimensions?
The key maximum case dimensions for the 400 Legend include a 1.650 inch case length, a 0.422 inch rebated rim diameter, a 0.440 inch base diameter, and a 0.4267 inch neck diameter at the case mouth.
What is the 400 Legend case length?
The maximum SAAMI case length for the 400 Legend is 1.650 inches (41.91 mm). The standard trim to length for reloading is 1.640 inches.
What is the 400 Legend rim diameter?
The 400 Legend features a rebated rim with a maximum diameter of 0.422 inches (10.72 mm), which matches a standard 6.8 SPC bolt face.
What is the 400 Legend base diameter?
The base diameter of the 400 Legend, measured just above the extractor groove, is 0.440 inches (11.18 mm).
What is the 400 Legend shoulder diameter?
The 400 Legend is a straight-walled cartridge and does not possess a shoulder.
What is the 400 Legend neck diameter?
The maximum outside neck diameter at the case mouth for the 400 Legend is 0.4267 inches (10.84 mm).
What is the 400 Legend case capacity?
The nominal case capacity of the 400 Legend is approximately 44.0 grains of water (H2O), or 2.85 cubic centimeters.
What is the 400 Legend overall length?
The maximum overall cartridge length (OAL) for the 400 Legend is 2.260 inches (57.40 mm) under SAAMI specifications.
How does 400 Legend compare with 350 Legend case dimensions?
The 400 Legend features a much wider 0.440 inch base compared to the 0.390 inch base of the 350 Legend. To fit the larger bullet within the same 2.260 inch overall magazine length, the 400 Legend case is slightly shorter at 1.650 inches compared to the 350 Legend case length of 1.710 inches.
Are 400 Legend and 350 Legend case dimensions the same?
No. The 400 Legend is significantly wider at the base (0.440 inches versus 0.390 inches) and utilizes a larger rim diameter (0.422 inches versus 0.378 inches). They are not interchangeable and require completely different bolt faces.
How does 400 Legend compare with 450 Bushmaster case dimensions?
The 400 Legend is narrower than the 450 Bushmaster. The 400 Legend uses a 0.440 inch base and a 0.422 inch rim. The 450 Bushmaster uses a massive 0.500 inch base and a 0.473 inch rim.
What is the 400 Legend maximum pressure?
The SAAMI maximum average pressure (MAP) for the 400 Legend is 45,000 psi (piezo method).