The key 300 PRC case dimensions include a maximum case length of 2.580 inches (65.53 mm) and a maximum overall cartridge length of 3.700 inches (93.98 mm). The case features a 0.532-inch rim diameter, a 0.532-inch base diameter, a 0.515-inch shoulder diameter, and a maximum neck diameter of 0.342 inches. The neck length measures approximately 0.308 inches to securely hold heavy .30-caliber projectiles. When reviewing these measurements, note that published dimensions may include nominal values, maximum limits, or specific tolerances depending on the specification source. These exact dimensions require a magnum-length rifle action to properly feed and cycle the long, high-ballistic-coefficient bullets the cartridge was engineered to fire.
300 PRC Case Dimensions
| Case Dimension | Inches | Millimeters | Specification Type | Source | Notes |
| Case Length | 2.580 | 65.53 | Maximum | SAAMI | Trim-to length is typically 2.570″ |
| Rim Diameter | 0.532 | 13.51 | Maximum | SAAMI | Matches standard magnum bolt faces |
| Base Diameter | 0.532 | 13.51 | Maximum | SAAMI | Beltless design; body is wider than belted magnums |
| Shoulder Diameter | 0.515 | 13.08 | Nominal Maximum | SAAMI | Provides minimal body taper for efficiency |
| Neck Diameter | 0.342 | 8.69 | Maximum | SAAMI | Accommodates a 0.308-inch projectile |
| Neck Length | ~0.308 | 7.82 | Nominal | Derived | Roughly equals one bullet diameter |
| Shoulder Angle | 30° | N/A | Nominal | SAAMI | Steeper than the 300 Win Mag |
| Overall Cartridge Length | 3.700 | 93.98 | Maximum | SAAMI | Requires a true magnum-length action |
| Case Capacity | ~88 to 97 gr H2O | ~5.70 to 6.28 cm³ | Measured Range | Industry / Mfg | Varies based on brass brand (Hornady, ADG, Bertram) |
| Maximum Pressure | 65,000 psi | 448 MPa | Maximum Average | SAAMI | Standardized high-pressure limit |
Understanding The 300 PRC Case Dimensions
To fully grasp how the 300 Precision Rifle Cartridge operates, it helps to understand what each specific measurement dictates inside the firearm:
- Case length: Measured from the base of the rim to the case mouth, this dictates how far the brass extends into the chamber.
- Rim diameter: The width of the extraction rim at the very bottom of the case. It utilizes the standard 0.532-inch magnum rim, allowing compatibility with existing magnum bolt faces.
- Base diameter: The width of the case body just above the extractor groove. The 300 PRC is beltless, meaning the body diameter stays at 0.532 inches rather than shrinking down ahead of a belt.
- Shoulder diameter: The width of the case right before it tapers inward. At 0.515 inches, the case has very little taper, maximizing powder capacity.
- Neck diameter: The outside diameter of the case mouth once a bullet is seated.
- Neck length: The straight portion of the case that grips the bullet. A neck length of roughly 0.308 inches ensures adequate neck tension for long, heavy projectiles.
- Shoulder geometry:The 30-degree angle that stops the cartridge in the chamber, establishing proper headspace.
- Overall cartridge length: The total length of the assembled round (brass plus bullet). This must not exceed 3.700 inches to feed reliably from magnum magazines.
- Case capacity: The internal volume of the case, typically measured in grains of water (H2O), dictating how much powder can be safely loaded.
300 PRC Case Dimensions In Inches And Millimeters
A reliable 300 PRC dimensions chart makes conversions simple. Here are the primary 300 PRC dimensions in mm and inches, reflecting official maximum and nominal tolerances:
| Dimension | Inches | Millimeters |
| Maximum Case Length | 2.580″ | 65.53 mm |
| Base Diameter | 0.532″ | 13.51 mm |
| Rim Diameter | 0.532″ | 13.51 mm |
| Shoulder Diameter | 0.515″ | 13.08 mm |
| Neck Diameter | 0.342″ | 8.69 mm |
| Overall Cartridge Length | 3.700″ | 93.98 mm |
300 PRC Case Length
The SAAMI maximum 300 PRC case length is standardized at 2.580 inches (65.53 mm). Under the intense pressure of firing (65,000 psi), fired and resized cases will flow and stretch. If the case elongates past 2.580 inches, the case mouth can pinch against the end of the chamber, dangerously spiking internal pressure. For this reason, reloaders typically use a “trim-to” length of 2.570 inches to ensure consistent chamber fit and safe ammunition performance.
300 PRC Base And Rim Dimensions
The 300 PRC utilizes a standard 0.532-inch magnum rim, which means it operates flawlessly with existing magnum bolt faces (such as those used for the 300 Win Mag or 7mm Rem Mag). However, the critical difference is the base diameter. Traditional belted magnums shrink down ahead of the belt, but the 300 PRC is a beltless design. The base diameter remains at a robust 0.532 inches just ahead of the extractor groove, granting the cartridge superior powder capacity and smoother feeding characteristics.
300 PRC Shoulder And Neck Dimensions
The 300 PRC uses a modernized 30-degree shoulder angle.The shoulder diameter sits at 0.515 inches, which prevents excessive body taper and promotes uniform powder ignition. The case steps down to a maximum neck diameter of 0.342 inches to securely hold a 0.308-inch projectile. This geometry establishes extremely precise headspacing on the shoulder rather than a belt, which aligns the cartridge perfectly with the bore for enhanced accuracy.
300 PRC Case Capacity
Internal 300 PRC case capacity is vast but not entirely uniform across manufacturers. Depending on the brass brand and the thickness of the case walls, capacity typically ranges between 88 and 97 grains of water (H2O).
Hornady brass typically offers a higher capacity closer to 97 grains, while thicker-walled brass from boutique manufacturers like Bertram may measure closer to 88 or 89 grains. This variance is critical for reloaders, as swapping from a high-capacity case to a low-capacity case without reducing the powder charge can result in dangerous overpressure spikes.
300 PRC Case Dimensions vs 300 Win Mag
While both fire .30-caliber projectiles, the 300 PRC was designed to solve the dimensional shortcomings of the older 300 Win Mag. Below is a dimensional comparison:
| Dimension | 300 PRC | 300 Win Mag | Source |
| Case Length | 2.580″ (65.53 mm) | 2.620″ (66.55 mm) | SAAMI |
| Rim Diameter | 0.532″ (13.51 mm) | 0.532″ (13.51 mm) | SAAMI |
| Base Diameter | 0.532″ (beltless) | 0.513″ (ahead of belt) | SAAMI |
| Shoulder Diameter | 0.515″ (13.08 mm) | 0.489″ (12.42 mm) | SAAMI |
| Neck Diameter | 0.342″ (8.69 mm) | 0.339″ (8.61 mm) | SAAMI |
| Overall Cartridge Length | 3.700″ (93.98 mm) | 3.340″ (84.84 mm) | SAAMI |
| Case Capacity | ~88 to 97 gr H2O | ~90 to 95 gr H2O | Industry Data |
Note: The 300 Win Mag has a longer brass case (2.620 inches) but a much shorter overall cartridge length (3.340 inches).This forces long, heavy bullets to be seated deeply inside the 300 Win Mag case, eating up powder capacity.The 300 PRC utilizes a slightly shorter brass case (2.580 inches) but a significantly longer overall length (3.700 inches), allowing heavy bullets to sit far out of the powder column.
300 PRC Case Dimensions vs 300 Norma Mag
The 300 Norma Mag is another modern .30-caliber heavy hitter, but it is built on a much wider parent case (the .338 Lapua Magnum).
| Dimension | 300 PRC | 300 Norma Mag | Source |
| Case Length | 2.580″ (65.53 mm) | 2.492″ (63.30 mm) | SAAMI |
| Rim Diameter | 0.532″ (13.51 mm) | 0.588″ (14.94 mm) | SAAMI |
| Base Diameter | 0.532″ (13.51 mm) | 0.583″ (14.81 mm) | SAAMI |
| Shoulder Diameter | 0.515″ (13.08 mm) | 0.569″ (14.45 mm) | SAAMI |
| Neck Diameter | 0.342″ (8.69 mm) | 0.343″ (8.71 mm) | SAAMI |
| Overall Cartridge Length | 3.700″ (93.98 mm) | 3.681″ (93.50 mm) | SAAMI |
| Case Capacity | ~88 to 97 gr H2O | ~104 gr H2O | Industry Data |
Because the 300 Norma Mag features a massive 0.588-inch rim, it requires a larger, specialized Lapua magnum bolt face. The 300 PRC is far easier to adopt because it utilizes the standard 0.532-inch magnum bolt face common to countless factory rifles.
300 PRC Cartridge And Chamber Dimensions
A firearm’s chamber must precisely mirror the cartridge to ensure safety and accuracy. The 300 PRC chamber was drafted with a highly specialized throat to accommodate long-range bullets.The SAAMI specification includes a long freebore (approximately 0.238 inches) with a tight diameter that measures only slightly larger than the bullet itself (0.3088 inches).
This tight clearance guarantees the bullet is perfectly aligned with the rifling before it fully leaves the case neck. Furthermore, by headspacing off the 30-degree case shoulder rather than a belt, the cartridge remains perfectly centered in the chamber, which drastically improves extreme long-range precision.
300 PRC Case Forming And Resizing
The 300 PRC was developed by modifying the .375 Ruger case. Conceptually, producing 300 PRC brass from a .375 Ruger involves necking down the brass from .375 caliber to .308 caliber and slightly pushing the shoulder back. This parent-case relationship is why the 300 PRC retains the beltless 0.532-inch base diameter of the Ruger Compact Magnum family.
Manufacturer Specifications vs Actual Measurements
When researching 300 PRC dimensions, it is critical to distinguish between maximum specifications and actual measurements. SAAMI dictates a maximum average pressure of 65,000 psi.
Similarly, the SAAMI maximum case length is 2.580 inches. If you measure a brand new factory cartridge with calipers, you will often find it measures closer to 2.570 inches. Manufacturers intentionally produce brass slightly under the absolute maximum limit. This built-in tolerance guarantees that their ammunition will chamber easily and safely across a vast array of different rifle brands, accounting for minor chamber variations.
Common Questions
What are the 300 PRC case dimensions?
Key dimensions include a 2.580-inch maximum case length, 0.532-inch rim diameter, 0.532-inch base diameter, 0.515-inch shoulder diameter, and a 0.342-inch maximum neck diameter.
What is the 300 PRC case length?
The official SAAMI maximum case length for the 300 PRC is 2.580 inches (65.53 mm).
What is the 300 PRC base diameter?
The nominal base diameter is 0.532 inches, matching its rim diameter due to its beltless design.
What is the 300 PRC rim diameter?
The rim diameter is 0.532 inches, allowing it to utilize standard magnum bolt faces.
What is the 300 PRC shoulder diameter?
The shoulder diameter measures 0.515 inches, meeting the neck at a 30-degree angle.
What is the 300 PRC neck diameter?
The maximum neck diameter is 0.342 inches.
What is the 300 PRC case capacity?
Depending on the brass manufacturer and wall thickness, capacity ranges from roughly 88 to 97 grains of water (H2O).
How does 300 PRC case size compare with 300 Win Mag?
The 300 PRC has a slightly shorter case length (2.580 inches vs 2.620 inches), but it lacks a belt, features a wider body taper, and has a significantly longer overall assembled cartridge length (3.700 inches vs 3.340 inches).This allows the 300 PRC to seat heavy bullets further out of the powder column.
What is the 300 PRC overall cartridge length?
The maximum overall cartridge length (OAL) is 3.700 inches (93.98 mm), requiring a magnum-length rifle action.
What is the 300 PRC maximum pressure?
The SAAMI maximum average pressure for the 300 PRC is 65,000 psi.