The exact .300 PRC (Precision Rifle Cartridge) bullet diameter is 0.308 inches, which converts to 7.82 millimeters. While .300 PRC ammunition is available with different bullet weights, the cartridge’s nominal projectile diameter remains exactly the same across all factory loads. This measurement refers specifically to the width of the bullet itself, which differs from the internal dimensions of the barrel. Specifically, a standard .300 PRC firearm utilizes a narrower bore diameter of 0.300 inches and a groove diameter of 0.308 inches to ensure a tight gas seal upon firing.
.300 PRC Bullet Diameter
| Specification | .300 PRC |
| Nominal Bullet Diameter | 0.308 inches |
| Bullet Diameter In Inches | 0.308″ |
| Bullet Diameter In Millimeters | 7.82 mm |
| Groove Diameter | 0.308 inches |
| Bore Diameter | 0.300 inches |
| Typical Bullet Weights | 212 gr to 250 gr |
| Case Length | 2.585 inches |
| Overall Cartridge Length | 3.700 inches |
| Maximum Pressure (SAAMI) | 65,000 PSI |
What Is The .300 PRC Bullet Diameter?
The .300 PRC bullet diameter is the physical width of the unfired projectile seated in the cartridge case. Developed by Hornady and adopted by the U.S. military for long-range sniper applications, the .300 PRC was introduced in 2018. It was specifically engineered around long, heavy, high-BC (ballistic coefficient) .30-caliber bullets to maximize aerodynamic efficiency, precision, and consistency at extreme distances well beyond 1,000 yards.
.300 PRC Bullet Diameter In Inches
According to the official Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) specifications, the .300 PRC bullet diameter in inches is standard at 0.308 inches. Because it shares the universal .30-caliber standard, it utilizes the exact same bullet width as legendary rounds like the .308 Winchester, .30-06 Springfield, and .300 Winchester Magnum.
.300 PRC Bullet Diameter In Millimeters
For those using metric measurements, the .300 PRC bullet diameter in mm is 7.82 mm. Because 1 inch equals 25.4 millimeters, multiplying a 0.308-inch bullet by 25.4 yields exactly 7.8232 mm, which rounds cleanly to 7.82 mm.
.300 PRC Bullet vs Bore Diameter
A common point of confusion is the difference between the bullet’s width and the barrel’s internal dimensions. The .300 PRC bore diameter is 0.300 inches. The bore diameter measures the distance directly across the “lands” (the raised portions of the rifling inside the barrel). The unfired .300 PRC projectile diameter (0.308″) is deliberately wider than the bore so the rifling can firmly bite into the bullet jacket, imparting the stabilizing spin required for extreme long-range accuracy.
.300 PRC Groove Diameter
The .300 PRC groove diameter measures 0.308 inches. The groove diameter measures the distance across the deepest cuts inside the rifled barrel. When the 0.308-inch bullet is fired, it swages into the barrel and completely fills the 0.308-inch grooves. This creates a tight pressure seal that traps the expanding powder gases directly behind the bullet, preventing velocity loss and maintaining stable flight.
.300 PRC Bullet Weights
While the cartridge diameter is fixed at 0.308 inches, the .300 PRC is optimized for exceptionally heavy projectile masses. The .300 PRC bullet weight typically ranges from 212 grains up to massive 250-grain high-BC match and hunting bullets. These heavy payloads are seated long out of the case neck to prevent them from intruding into the powder space, maintaining consistent velocities and flat trajectories.
Bullet Diameter vs Other Cartridges
Shooters must be careful when comparing caliber names, as different cartridges frequently share identical bullet diameters despite varying case capacities. Here is how the .300 PRC compares to other prominent .30-caliber and long-range rounds:
| Cartridge | Bullet Diameter | Diameter In mm |
| .300 PRC | 0.308″ | 7.82 mm |
| .300 Winchester Magnum | 0.308″ | 7.82 mm |
| .308 Winchester | 0.308″ | 7.82 mm |
| 6.5mm Creedmoor | 0.264″ | 6.71 mm |
| .338 Lapua Magnum | 0.338″ | 8.59 mm |
Notice that the .300 PRC shares an identical 0.308-inch bullet diameter with the .300 Win Mag and standard .308 Winchester, but utilizes a significantly larger, modern rimless beltless case designed to feed ultra-long, high-efficiency bullets correctly aligned in the chamber.
Bullet Weight
Ammunition manufacturers produce specialized high-performance loads for the .300 PRC, heavily tailored for extreme long-range target shooting and big-game hunting.
| Bullet Weight | Example Load | Bullet Type | Advertised Velocity |
| 212 grain | Hornady ELD-X | Polymer-Tipped Hunting | 2,860 fps |
| 225 grain | Hornady ELD Match | Polymer-Tipped Target | 2,810 fps |
| 250 grain | Hornady A-Tip Match | Aluminum-Tipped Match | 2,700 fps |
Velocities represent typical factory test barrel data, generally from a 24-inch or 26-inch precision rifle barrel.
Dimensions
To understand how the cartridge fits into long-action precision rifles, here are the complete SAAMI-verified .300 PRC dimensions:
| Dimension | Measurement |
| Bullet Diameter | 0.308″ |
| Groove Diameter | 0.308″ |
| Bore Diameter | 0.300″ |
| Case Length | 2.585 inches |
| Overall Length | 3.700 inches |
| Base Diameter | 0.585 inches |
| Neck Diameter | 0.340 inches |
| Rim Diameter | 0.532 inches |
| Maximum Pressure (SAAMI) | 65,000 PSI |
.300 PRC vs .300 Winchester Magnum
Because both are prominent .30-caliber magnum rifle cartridges, shooters frequently compare the .300 PRC and the legacy .300 Winchester Magnum (.300 Win Mag).
Despite sharing the same 0.308-inch bullet diameter, they have vastly different design philosophies:
- Bullet Seating and Geometry: The .300 Win Mag was designed decades ago to fit within traditional standard-length rifle actions, forcing heavy bullets to be seated deeply into the powder column. The .300 PRC was designed from the ground up as a modern cartridge with a longer overall length (3.700″ vs 3.340″ for .300 Win Mag), allowing very long, aerodynamic, high-BC bullets to be seated out where they belong without robbing case capacity.
- Accuracy and Consistency: The .300 PRC features a tighter, straighter chamber design with a 30-degree shoulder engineered to self-center the cartridge perfectly upon chambering, yielding superior consistency and extreme long-range precision compared to the older belted design of the .300 Win Mag.
.300 PRC Bullet Diameter: Exact Measurement
The exact .300 PRC bullet diameter is 0.308 inches, or 7.82 millimeters.
While the actual projectile measures 0.308 inches across, it is forced through a barrel with a 0.300-inch bore diameter and a 0.308-inch groove diameter. This intentional sizing ensures the bullet squeezes tightly into the barrel’s rifling grooves. This physical engagement creates a reliable gas seal behind the projectile, preventing the 65,000 PSI of high-pressure expanding gases from blowing past the bullet while stabilizing heavy, ultra-aerodynamic target bullets for unmatched precision at extreme distances.
FAQs
What is the bullet diameter of .300 PRC?
The nominal bullet diameter is 0.308 inches.
What is .300 PRC bullet diameter in mm?
In metric measurements, the diameter translates to 7.82 mm.
Is .300 PRC a true .30 caliber?
Yes. Despite having “300” in the name, it fires a standard 0.308-inch projectile, making it a true .30-caliber cartridge.
What is the bore diameter of .300 PRC?
The barrel’s internal bore diameter (measured land-to-land) is 0.300 inches.
What is the groove diameter of .300 PRC?
The barrel’s internal groove diameter (measured groove-to-groove) is 0.308 inches.
What bullet weights are available for .300 PRC?
Factory loads typically feature heavy, high-performance match and hunting bullets ranging from 212 grains up to 250 grains.
What is privacy or case dimensions of .300 PRC?
The case is a rimless magnum design with a base diameter of 0.585 inches and a total case length of 2.585 inches.
How does .300 PRC bullet diameter compare with .300 Win Mag?
Both cartridges use the exact same 0.308-inch bullet diameter, but the .300 PRC is optimized for longer, heavier, high-BC bullets.