The .50 Beowulf is a rebated rim, straight walled centerfire rifle cartridge featuring a standard maximum bullet diameter of 0.500 inches (12.70 mm). The maximum case length is 1.650 inches (41.91 mm), and the maximum overall cartridge length is restricted to 2.260 inches (57.40 mm) to ensure compatibility with standard AR-15 magazines. The case utilizes a rebated rim diameter of 0.445 inches (11.30 mm) and features a wide base diameter of 0.535 inches (13.59 mm) that tapers very slightly to a 0.525 inch (13.34 mm) case mouth. Ammunition for this caliber is highly versatile, most commonly found in 300 grain to 400 grain supersonic bullet weights, along with massive subsonic options. Exact measurements and operating pressures rely on industry standards established by its creator, Alexander Arms, as the cartridge is not currently standardized by SAAMI or C.I.P.
.50 Beowulf Dimensions
| Dimension | Specification | Source | Notes |
| Bullet Diameter | 0.500 in (12.70 mm) | Industry | Standard for true .50 caliber rifle and pistol projectiles. |
| Case Length | 1.650 in (41.91 mm) | Industry | Maximum case length. |
| Overall Cartridge Length | 2.260 in (57.40 mm) | Industry | Maximum overall length for standard AR-15 magazines. |
| Rim Diameter | 0.445 in (11.30 mm) | Industry | Matches the standard 7.62x39mm or 6.5 Grendel bolt face. |
| Case Diameter (Base) | 0.535 in (13.59 mm) | Industry | Measured just above the extractor groove. |
| Shoulder Diameter | N/A | N/A | Straight walled cartridge, no shoulder. |
| Neck Diameter | 0.525 in (13.34 mm) | Industry | Maximum external diameter at the case mouth. |
| Base Diameter | 0.535 in (13.59 mm) | Industry | Wider than the rim, classifying it as a heavily rebated rim cartridge. |
| Case Capacity | ~ 65.8 gr H2O | Industry | Varies slightly based on the brass manufacturer. |
| Maximum Pressure | 33,000 psi | Industry | Governed by original design specifications for AR-15 bolt safety. |
Understanding The .50 Beowulf Dimensions
- Bullet Diameter: The measurement across the widest point of the bullet. For the .50 Beowulf, this is specified as exactly 0.500 inches. This massive dimension gives shooters access to a large inventory of heavy payload projectiles traditionally used in the .50 Action Express and .500 S&W Magnum.
- Case Length: The length of the empty brass cylinder from the base to the case mouth, maxing out at 1.650 inches. This incredibly short and fat case is essential to leave room in the magazine for massive .50 caliber projectiles.
- 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. This dimension guarantees the cartridge will fit inside a standard AR-15 magazine well without requiring a larger AR-10 receiver.
- Rim Diameter: The diameter of the flange at the very bottom of the case measuring 0.445 inches. The firearm extractor hooks onto this rim to pull the spent casing out of the chamber. Because it matches the 7.62x39mm and 6.5 Grendel, shooters must use an AR-15 bolt machined to match a 0.445 inch bolt face.
- Case Diameter: The width of the cartridge body at the base. At 0.535 inches, it is substantially wider than a standard 223 Remington, allowing it to hold enough gunpowder in a shortened package to cycle an AR-15 reliably.
- Base Diameter: The width of the brass just above the extractor groove. It must withstand the initial expansion of ignition.
- Maximum Pressure: Standard industry limits set this at 33,000 psi. This low pressure limit ensures that standard AR-15 bolt carrier groups do not suffer premature fatigue from the massive 0.535 inch case base pushing back against the locking lugs.
.50 Beowulf Cartridge Dimensions In Inches And Millimeters
For engineers, reloaders, and international shooters, below are the primary .50 Beowulf measurements converted accurately between imperial and metric systems.
| Dimension | Inches (Industry Max) | Millimeters (Equivalent) |
| Bullet Diameter | 0.500 in | 12.70 mm |
| Case Length | 1.650 in | 41.91 mm |
| Overall Length | 2.260 in | 57.40 mm |
| Rim Diameter | 0.445 in | 11.30 mm |
| Base Diameter | 0.535 in | 13.59 mm |
| Neck Diameter | 0.525 in | 13.34 mm |
.50 Beowulf Case Dimensions
The .50 Beowulf case was engineered by Alexander Arms by lengthening the .50 Action Express case and heavily rebating the rim to fit an AR-15 bolt. The official maximum case length is 1.650 inches (41.91 mm). The base diameter measures a massive 0.535 inches, while the rim diameter is cut much narrower to 0.445 inches.
This drastically widened case body is highly intentional. By pushing the brass out to 0.535 inches, ammunition manufacturers give the .50 Beowulf a massive internal powder capacity of approximately 65.8 grains of water. This large capacity allows the .50 Beowulf to push heavy bullets using relatively small charges of fast burning magnum pistol or shotgun powders. The case is straight walled with a microscopic taper to aid in extraction from dirty rifle chambers.
.50 Beowulf Bullet Diameter
The standardized maximum bullet diameter for the .50 Beowulf is 0.500 inches (12.70 mm). This is a critical distinction in the firearms world. While cartridges like the .450 Bushmaster and .458 SOCOM utilize 45 caliber projectiles, the .50 Beowulf maximizes the absolute physical limits of the AR-15 barrel extension by utilizing a true half inch projectile.
Adopting the 0.500 inch bore size gives reloaders access to an excellent inventory of bullets designed for the .500 S&W Magnum and .50 Action Express. Firing a 0.500 inch bullet down this barrel forces the thick copper jacket to engrave tightly into the rifling. To properly stabilize these massive, short bullets, barrels are typically manufactured with a 1 in 20 inch twist rate.
.50 Beowulf Overall Length
The maximum overall cartridge length (OAL) for the .50 Beowulf is 2.260 inches (57.40 mm). This number is a strict hard limit established by the physical internal dimensions of standard AR-15 magazine wells.
Because the .50 Beowulf cartridge uses massive bullets that can weigh up to 400 grains or more, the projectiles must be seated deeply into the case to stay under the 2.260 inch restriction. This limit makes the .50 Beowulf an incredible close range tactical and hunting tool, allowing users to shoot heavy hitting bullets from a standard lightweight AR-15. In standard 5.56 NATO magazines, the fat .50 Beowulf cartridges perfectly single stack, meaning a standard 30 round AR-15 magazine will reliably hold 10 rounds of .50 Beowulf without internal modifications, though specialized followers are often recommended.
.50 Beowulf Chamber And Cartridge Dimensions
The relationship between the .50 Beowulf cartridge and the firearm chamber is critical for reliable feeding. Because it is a straight walled cartridge, the .50 Beowulf headspaces on the case mouth.
This provides a positive stopping point inside the chamber, keeping the cartridge properly aligned with the bore. Because the .50 Beowulf operates at a relatively low 33,000 psi, it extends brass life significantly. Reloaders must carefully measure their brass, as cases that stretch beyond 1.650 inches will pinch in the chamber and cause pressure spikes. Because it headspaces on the case mouth, a taper crimp must be used rather than a roll crimp to secure the heavy bullets.
.50 Beowulf Dimensions vs Similar Cartridges
To understand the .50 Beowulf size profile, it is helpful to compare it against other popular big bore hunting and tactical cartridges.
| Cartridge | Bullet Diameter | Case Length | Overall Length | Rim / Base Diameter | Maximum Pressure | Source |
| .50 Beowulf | 0.500 in | 1.650 in | 2.260 in | 0.445 in / 0.535 in | 33,000 psi | Industry |
| 458 SOCOM | 0.458 in | 1.575 in | 2.260 in | 0.473 in / 0.541 in | 35,000 psi | Industry |
| 450 Bushmaster | 0.452 in | 1.700 in | 2.260 in | 0.473 in / 0.500 in | 38,500 psi | SAAMI |
| .500 S&W Mag | 0.500 in | 1.625 in | 2.300 in | 0.556 in / 0.526 in | 60,000 psi | SAAMI |
| 45-70 Government | 0.458 in | 2.105 in | 2.550 in | 0.608 in / 0.505 in | 28,000 psi | SAAMI |
.50 Beowulf vs 458 SOCOM Dimensions
The .50 Beowulf and the 458 SOCOM are two of the most popular big bore cartridges designed to maximize the AR-15 platform. While they both max out at a 2.260 inch overall length, their internal and external dimensions are vastly different.
- Bullet Diameter: The .50 Beowulf utilizes a massive 0.500 inch bullet. The 458 SOCOM uses a narrower 0.458 inch rifle bullet.
- Case Shape: The .50 Beowulf is a straight walled cartridge, headspacing on the case mouth. The 458 SOCOM is a bottlenecked cartridge, headspacing on a shoulder.
- Base and Rim: The .50 Beowulf uses a 0.535 inch base with a 0.445 inch rim (matching the 7.62x39mm bolt). The 458 SOCOM uses a wider 0.541 inch base with a 0.473 inch rim (matching the 308 Winchester bolt).
- Case Length: The .50 Beowulf features a longer 1.650 inch case compared to the 1.575 inch case of the 458 SOCOM.
.50 Beowulf Industry Specifications vs SAAMI
Cartridge dimensions and safe pressure limits in the United States are officially standardized by SAAMI. However, the .50 Beowulf is a proprietary cartridge developed by Bill Alexander of Alexander Arms and has not been submitted for SAAMI approval.
Because it lacks SAAMI standardization, ammunition manufacturers rely on agreed upon industry specifications provided by Alexander Arms. The maximum average pressure is strictly capped at 33,000 psi. This limit is enforced because the .50 Beowulf uses a wide 0.535 inch base pushing back against an AR-15 bolt that has been heavily milled out to accommodate the 0.445 inch rim. Exceeding 33,000 psi generates massive bolt thrust that can shear the locking lugs off the AR-15 bolt.
.50 Beowulf Bullet Weight And Dimensions
The .50 Beowulf was built to utilize extreme bullet weights for short range devastation, changing how the cartridge is dimensionally assembled:
- 300 to 350 grain: Factory options sit perfectly in the 1.650 inch case and deliver high velocities for close to medium range hunting and barrier penetration. Because they are physically shorter, they leave ample case capacity for standard powder charges.
- 400 grain: Extremely heavy projectiles optimized for deep penetration and energy transfer. To stay under the 2.260 inch magazine limit, these long, blunt bullets must be seated very deeply into the brass case, which significantly reduces the internal powder volume and requires careful reloading data.
Bullet weight does not change the standardized external brass case dimensions, but it heavily dictates the seating depth and internal powder capacity.
Why .50 Beowulf Dimensions Matter
Understanding the specific .50 Beowulf measurements is essential for several practical reasons.
- AR-15 Upgrades: Knowing the 0.445 inch rim diameter reminds builders that they need a specific 7.62x39mm or 6.5 Grendel bolt face to feed and extract the cartridge properly. A standard 5.56 NATO bolt will not fit over the cartridge rim.
- Hunting Regulations: Because it utilizes a 1.650 inch straight walled case, the .50 Beowulf is perfectly legal for hunting in Midwestern states that restrict rifle hunters to straight walled cartridges under 1.800 inches in length.
- Ejection Port Modifications: The massive 0.535 inch base diameter means the .50 Beowulf case is too fat to cleanly eject through a standard mil-spec AR-15 upper receiver. The ejection port must be physically milled open to safely clear the spent brass.
Manufacturer Specifications vs Independent Measurements
If you use calipers to measure factory .50 Beowulf ammunition from companies like Alexander Arms or Underwood Ammo, the numbers will rarely match the maximum specifications exactly.
Industry specifications publish 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 1.650 inches, but measuring a factory cartridge might reveal a case length of 1.640 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 .50 Beowulf?
The key maximum dimensions are a bullet diameter of 0.500 inches, a case length of 1.650 inches, and an overall cartridge length of 2.260 inches.
What is the .50 Beowulf case length?
The case length measures exactly 1.650 inches (41.91 mm).
What is the .50 Beowulf overall length?
The maximum overall length (OAL) is 2.260 inches (57.40 mm), designed to fit perfectly flush inside standard AR-15 magazines.
What is the .50 Beowulf bullet diameter?
The bullet diameter is exactly 0.500 inches (12.70 mm).
What is the .50 Beowulf rim diameter?
The rim diameter measures 0.445 inches, which matches a standard 7.62x39mm or 6.5 Grendel AR-15 bolt face.
What is the .50 Beowulf case capacity?
The .50 Beowulf holds approximately 65.8 grains of water, giving it a massive capacity for an AR-15 platform cartridge.
What is the maximum pressure for the .50 Beowulf?
The industry maximum average pressure is strictly capped at 33,000 psi for safe operation in AR-15 rifles.
How do .50 Beowulf and 458 SOCOM dimensions compare?
They share the same 2.260 inch maximum overall length, but the .50 Beowulf uses a straight walled 0.535 inch base and a larger 0.500 inch bullet, compared to the bottlenecked 0.541 inch base and 0.458 inch bullet of the 458 SOCOM.
Is the .50 Beowulf SAAMI approved?
No. The .50 Beowulf is a proprietary cartridge and operates on agreed upon industry specifications originally established by Alexander Arms.