The 300 Precision Rifle Cartridge (300 PRC) is a beltless magnum centerfire rifle cartridge featuring a standard maximum bullet diameter of 0.308 inches (7.82 mm). The maximum case length is 2.580 inches (65.53 mm), and the maximum overall cartridge length (OAL) is specified at a massive 3.700 inches (93.98 mm) to accommodate extremely long and aerodynamic bullets. The case utilizes a standard magnum rim diameter of 0.532 inches (13.51 mm) and a matching base diameter of 0.532 inches (13.51 mm). Ammunition for this caliber is most commonly found in heavy 212 grain and 225 grain bullet weights. Exact dimensions and operating pressures can vary slightly depending on allowable manufacturing tolerances and whether you reference American SAAMI specifications or European C.I.P. standards.
300 PRC Dimensions
| Dimension | Specification | Source | Notes |
| Bullet Diameter | 0.308 in (7.82 mm) | SAAMI | Standard for .30 caliber projectiles. |
| Case Length | 2.580 in (65.53 mm) | SAAMI | Maximum case length; trim to length is typically 2.570 in. |
| Overall Cartridge Length | 3.700 in (93.98 mm) | SAAMI | Maximum overall length for magnum rifle actions. |
| Rim Diameter | 0.532 in (13.51 mm) | SAAMI | Standard magnum bolt face dimension. |
| Case Diameter (Base) | 0.532 in (13.51 mm) | SAAMI | Measured just above the extractor groove. |
| Shoulder Diameter | 0.515 in (13.08 mm) | SAAMI | Features a modern 30 degree shoulder angle. |
| Neck Diameter | 0.344 in (8.74 mm) | SAAMI | Maximum external diameter at the case mouth. |
| Base Diameter | 0.532 in (13.51 mm) | SAAMI | Uniform with the rim to eliminate the traditional magnum belt. |
| Case Capacity | 90.0 to 92.0 gr H2O | Industry | Varies slightly based on the brass manufacturer and wall thickness. |
| Maximum Pressure | 65,000 psi | SAAMI | Governed by SAAMI specifications for modern magnum rifles. |
Understanding The 300 PRC Dimensions
- Bullet Diameter: The measurement across the widest point of the bullet. For the 300 PRC, this is specified as 0.308 inches. This dimension ensures the projectile seals properly within the barrel rifling to trap expanding gases and generate extreme long range velocity.
- Case Length: The length of the empty brass cylinder from the base to the case mouth, maxing out at 2.580 inches. This extended case provides the massive internal volume needed to push heavy .30 caliber bullets at magnum speeds.
- Overall Cartridge Length (OAL): The total length of the fully assembled round from the base to the tip of the bullet, heavily extended to 3.700 inches. This extreme length dictates that the 300 PRC requires a true magnum length action to feed and eject properly.
- Rim Diameter: The diameter of the flange at the very bottom of the case measuring 0.532 inches. This is the exact same rim diameter used by traditional belted magnums, meaning rifle builders can use standard magnum bolt faces.
- Case Diameter: The width of the cartridge body at the base. By matching the base diameter (0.532 inches) to the rim diameter, Hornady eliminated the need for a traditional brass belt.
- Shoulder Diameter: The width of the case where it begins to angle inward toward the neck (0.515 inches). The 300 PRC utilizes a steep 30 degree shoulder to optimize powder burn efficiency and control brass stretching.
- Case Capacity: Measured in grains of water (gr H2O), this represents the internal volume of the empty case. Averaging roughly 90 to 92 grains of water, this cartridge holds enough slow burning powder to propel heavy bullets efficiently.
- Maximum Pressure: The peak internal pressure generated when the cartridge is fired. Standard SAAMI limits set this at a robust 65,000 psi.
300 PRC Cartridge Dimensions In Inches And Millimeters
For engineers, reloaders, and international shooters, below are the primary 300 PRC measurements converted accurately between imperial and metric systems.
| Dimension | Inches (SAAMI Max) | Millimeters (Equivalent) |
| Bullet Diameter | 0.308 in | 7.82 mm |
| Case Length | 2.580 in | 65.53 mm |
| Overall Length | 3.700 in | 93.98 mm |
| Rim Diameter | 0.532 in | 13.51 mm |
| Base Diameter | 0.532 in | 13.51 mm |
| Shoulder Diameter | 0.515 in | 13.08 mm |
| Neck Diameter | 0.344 in | 8.74 mm |
300 PRC Case Dimensions
The 300 PRC is defined by a massive, beltless, bottlenecked case derived directly from the 375 Ruger parent case. The official maximum case length is 2.580 inches (65.53 mm), with a nominal trim to length for reloaders sitting at 2.570 inches. The base diameter measures 0.532 inches, blending seamlessly into the 0.532 inch rim.
Because the 300 PRC case eliminates the traditional magnum belt found on older cartridges, it offers superior chamber alignment. The case walls expand perfectly centered within the chamber. The steep 30 degree shoulder angle also prevents the brass from flowing forward into the neck during firing, which drastically extends the reloading life of the brass and maintains consistent internal case capacity around 90 grains of water.
300 PRC Bullet Diameter
The standardized maximum bullet diameter for the 300 PRC is 0.308 inches (7.82 mm). This is a massive advantage because 0.308 caliber bullets are among the most technologically advanced and widely available projectiles on the global market.
The standard 300 PRC barrel features a groove diameter of 0.308 inches and a bore or land diameter of 0.300 inches. Firing a 0.308 inch bullet down a 0.300 inch bore diameter forces the copper jacket to engrave tightly into the rifling. The 300 PRC is typically chambered in barrels with fast twist rates, such as 1:8 or 1:8.5, to properly stabilize modern bullets that are exceptionally long and heavy.
300 PRC Overall Length
The SAAMI maximum overall cartridge length (OAL) for the 300 PRC is 3.700 inches (93.98 mm). This massive overall length is the defining dimensional characteristic of the cartridge.
Historically, older magnum cartridges were restricted to a 3.340 inch OAL to fit inside standard long action magazines. This forced manufacturers to seat long, aerodynamic bullets dangerously deep inside the brass case, which displaced gunpowder and compromised accuracy. The 300 PRC ignores this older limitation completely. By pushing the OAL to 3.700 inches, the 300 PRC allows massive 225 grain bullets to sit entirely forward of the powder column. This maximizes powder capacity and ensures the bullet enters the barrel rifling perfectly aligned.
300 PRC Chamber And Cartridge Dimensions
The relationship between the 300 PRC cartridge and the firearm chamber is engineered for extreme precision. Unlike older belted magnums that headspace inconsistently on a brass belt, the 300 PRC headspaces entirely on its 30 degree shoulder.
This means the angled portion of the brass casing physically stops against a matching machined angle inside the barrel chamber. This provides a precise, solid stopping point that aligns the bullet perfectly concentric to the bore. Because the cartridge is designed for heavy target bullets, the chamber throat or leade is cut much longer than traditional hunting rifles to accommodate the elongated ogive of modern match projectiles without jamming them into the lands.
300 PRC Dimensions vs Similar Cartridges
To understand the 300 PRC size profile, it is helpful to compare it against other popular 30 caliber magnum rifle cartridges.
| Cartridge | Bullet Diameter | Case Length | Overall Length | Base Diameter | Maximum Pressure | Source |
| 300 PRC | 0.308 in | 2.580 in | 3.700 in | 0.532 in | 65,000 psi | SAAMI |
| 300 Win Mag | 0.308 in | 2.620 in | 3.340 in | 0.513 in | 64,000 psi | SAAMI |
| 300 Norma Mag | 0.308 in | 2.492 in | 3.681 in | 0.587 in | 63,816 psi | C.I.P. |
| 300 RUM | 0.308 in | 2.850 in | 3.600 in | 0.550 in | 65,000 psi | SAAMI |
| 300 WSM | 0.308 in | 2.100 in | 2.860 in | 0.555 in | 65,000 psi | SAAMI |
300 PRC vs 300 Winchester Magnum Dimensions
The 300 PRC was designed specifically to fix the dimensional shortcomings of the legendary 300 Winchester Magnum. While both fire the exact same 0.308 inch bullets, their cases are fundamentally different.
- Overall Length: The 300 Win Mag is artificially limited to a 3.340 inch OAL to fit older military actions. The 300 PRC extends this to 3.700 inches, allowing modern bullets to be seated correctly without robbing powder capacity.
- Case Design: The 300 Win Mag utilizes a brass belt near the base for headspacing, which can cause inconsistent chamber alignment and reduced brass life. The 300 PRC is completely beltless and headspaces cleanly on its shoulder.
- Neck Length: The 300 Win Mag has a notoriously short case neck that fails to hold heavy bullets securely. The 300 PRC features a longer neck designed specifically to grip heavy 212 grain and 225 grain bullets with perfect concentricity.
300 PRC SAAMI vs C.I.P. Dimensions
Cartridge dimensions and safe pressure limits are governed by SAAMI in the United States and C.I.P. in Europe.
Hornady successfully submitted the 300 PRC to SAAMI for standardization in 2018. SAAMI lists the maximum average pressure for the 300 PRC at 65,000 psi, measured via conformal piezoelectric transducers. C.I.P. also adopted the cartridge, and while they measure pressure slightly differently, the physical dimensional specifications remain identical to ensure global compatibility. Ammunition manufactured to SAAMI specifications is considered safe and standard in any properly chambered rifle worldwide.
300 PRC Bullet Weight And Dimensions
The 300 PRC was optimized entirely around the longest, heaviest bullets available in the 30 caliber spectrum. Common factory bullet weights include:
- 212 grain: Typically loaded in the Hornady ELD-X line for extreme long range hunting. These bullets offer incredible ballistic coefficients and fit perfectly within the 3.700 inch overall length limit while leaving maximum case capacity for gunpowder.
- 225 grain: Typically loaded in the Hornady ELD Match line for competitive shooting. These massive bullets take full advantage of the extended chamber throat, staying supersonic well past 1,500 yards.
- 230 to 250 grain: Custom solid brass or ultra heavy target bullets used by handloaders. The 3.700 inch OAL of the 300 PRC easily accommodates these monolithic projectiles.
Bullet weight does not alter the external brass case dimensions, but the manufacturer must carefully manage bullet seating depth to ensure the loaded round takes full advantage of the magnum length magazine.
Why 300 PRC Dimensions Matter
Understanding the specific 300 PRC measurements is essential for several practical reasons.
- Action Size Requirements: The 3.700 inch overall length means shooters cannot simply rebarrel a standard long action rifle (like a 30-06 Springfield) to 300 PRC. The cartridge strictly requires a magnum length action, commonly referred to as a CIP length action, to feed reliably.
- Magazine Selection: Shooters building custom precision rifles must purchase specialized AICS CIP length magazines to accommodate the massive overall length of the cartridge.
- Reloading Consistency: Because the case headspaces precisely on the 30 degree shoulder without a belt, reloaders can easily bump the shoulder back a mere 0.002 inches during resizing. This exact dimensional control creates incredibly accurate ammunition with long brass life.
Manufacturer Specifications vs Independent Measurements
If you use precision calipers to measure factory 300 PRC ammunition from companies like Hornady or Federal, the numbers will rarely match the SAAMI maximum specifications exactly.
SAAMI publishes maximum allowable dimensions to ensure absolute safety and interoperability across all custom rifle builders. Ammunition manufacturers purposefully produce their cases slightly smaller than these maximums. For example, the maximum case length is 2.580 inches, but measuring a factory cartridge might reveal a case length of 2.568 inches. This built in negative tolerance margin guarantees that the massive ammunition will chamber smoothly in the field without jamming in tight match grade chambers.
Common Questions
What are the dimensions of the 300 PRC?
The key maximum dimensions are a bullet diameter of 0.308 inches, a case length of 2.580 inches, and a massive overall cartridge length of 3.700 inches.
What is the 300 PRC case length?
The maximum SAAMI case length is 2.580 inches (65.53 mm).
What is the 300 PRC overall length?
The maximum overall length (OAL) is 3.700 inches (93.98 mm), requiring a magnum length rifle action.
What is the 300 PRC bullet diameter?
The SAAMI maximum bullet diameter is 0.308 inches.
What is the 300 PRC rim diameter?
The rim diameter measures 0.532 inches, matching the standard magnum bolt face used by cartridges like the 300 Win Mag.
What is the 300 PRC case capacity?
The 300 PRC holds approximately 90.0 to 92.0 grains of water depending on the exact thickness of the specific brass casing.
What is the maximum pressure for the 300 PRC?
The SAAMI maximum average pressure is strictly capped at 65,000 psi.
How do 300 PRC and 300 Win Mag dimensions compare?
They share the same rim diameter (0.532 in) and bullet diameter (0.308 in), but the 300 PRC removes the brass belt, utilizes a longer 3.700 inch overall length, and features a modernized 30 degree shoulder.
Does the 300 PRC use the same bolt face as a 300 Win Mag?
Yes. Both cartridges share the exact same 0.532 inch magnum rim diameter, allowing them to utilize the same bolt carrier group and extractor mechanisms.