The 25 Creedmoor is a rimless, bottlenecked centerfire rifle cartridge featuring a standard maximum bullet diameter of 0.257 inches (6.53 mm).The maximum case length is 1.920 inches (48.77 mm), and the maximum overall cartridge length (COAL) is standardized by SAAMI at 2.825 inches (with specific factory match loads commonly loaded to 2.810 inches) to ensure seamless feeding from standard short-action internal boxes and AICS-style detachable magazines. The case utilizes a rim diameter of 0.473 inches (12.01 mm) and features a base diameter of 0.470 inches (11.94 mm) that tapers to a 30-degree shoulder measuring 0.462 inches (11.73 mm). Factory ammunition is optimized around high-BC, long-range “quarter-bore” bullets ranging from 117 grains to heavy 134–138 grain match projectiles.
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25 Creedmoor Dimensions
| Dimension | Specification | Source | Notes |
| Bullet Diameter | 0.257 in (6.53 mm) | SAAMI | Standard for .25 caliber (quarter-bore) rifle projectiles. |
| Case Length | 1.920 in (48.77 mm) | SAAMI | Maximum case length; trim-to length is typically 1.910 in. |
| Overall Cartridge Length | 2.825 in (71.76 mm) | SAAMI | Maximum allowable overall length; factory match rounds often set to 2.810 in. |
| Rim Diameter | 0.473 in (12.01 mm) | SAAMI | Matches the standard Creedmoor / .308 Winchester bolt face. |
| Case Diameter (Base) | 0.470 in (11.94 mm) | SAAMI | Measured just above the extractor groove. |
| Shoulder Diameter | 0.462 in (11.73 mm) | SAAMI | Features a sharp 30-degree shoulder angle. |
| Neck Diameter | 0.288 in (7.32 mm) | SAAMI | Maximum external diameter at the case mouth. |
| Case Capacity | ~ 52.5 gr H2O | Industry Standard | Inherited from the standard 6.5mm Creedmoor parent case footprint. |
| Maximum Pressure | 62,000 psi | SAAMI | Governed by SAAMI standards for high-pressure short-action platforms. |
Understanding The 25 Creedmoor Dimensions
- Bullet Diameter: The measurement across the widest point of the bullet. For the 25 Creedmoor, this is 0.257 inches, reviving the classic .25 caliber (quarter-bore) class with modern, high-efficiency aerodynamic designs.
- Case Length: Maxing out at 1.920 inches, the brass length is identical to both the 6mm and 6.5mm Creedmoor variants, sharing the same basic case body architecture.
- Overall Cartridge Length (OAL):Standardized up to a maximum of 2.825 inches.This length takes advantage of short-action magazine boxes, allowing sleek, high-BC long-range bullets to be seated cleanly without intruding excessively into the powder reservoir.
- Rim and Base Diameter: Measuring 0.473 inches at the rim, it relies on the standard .308 Winchester bolt face family, meaning it can be adapted easily to existing bolt-action or gas-gun architectures.
- Shoulder Angle: Incorporates a sharp 30-degree shoulder, promoting uniform flame propagation, reducing case growth during firing cycles, and ensuring repeatable headspacing.
- Maximum Pressure:Capped safely at 62,000 psi by SAAMI standards.When paired with low-drag .25 caliber projectiles, this pressure yields velocities that bridge the recoil characteristics of a 6mm with wind-bucking performance tracking close to or exceeding traditional 6.5mm loads.
25 Creedmoor Cartridge Dimensions In Inches And Millimeters
For engineers, handloaders, and precision shooters, below are the primary 25 Creedmoor measurements converted accurately between imperial and metric systems.
| Dimension | Inches (SAAMI Max) | Millimeters (Equivalent) |
| Bullet Diameter | 0.257 in | 6.53 mm |
| Case Length | 1.920 in | 48.77 mm |
| Overall Length (Max) | 2.825 in | 71.76 mm |
| Rim Diameter | 0.473 in | 12.01 mm |
| Base Diameter | 0.470 in | 11.94 mm |
| Shoulder Diameter | 0.462 in | 11.73 mm |
| Neck Diameter | 0.288 in | 7.32 mm |
25 Creedmoor Case Dimensions Overview
| Dimension Property | Specification (Imperial) | Specification (Metric) |
| Parent Case | 6-5 Creedmoor | 6-5 Creedmoor |
| Bullet Diameter | 257 thousandths in | 6 mm and 53 hundredths mm |
| Case Length | 1 in and 920 thousandths | 48 mm and 77 hundredths |
| Case Trim Length | 1 in and 910 thousandths | 48 mm and 51 hundredths |
| Overall Length (COAL) | 2 in and 825 thousandths (Max) | 71 mm and 76 hundredths |
| Rim Diameter | 473 thousandths in | 12 mm and 1 hundredth |
| Rim Thickness | 54 thousandths in | 1 mm and 37 hundredths |
| Base Diameter | 4703 ten-thousandths in | 11 mm and 95 hundredths |
| Shoulder Diameter | 462 thousandths in | 11 mm and 73 hundredths |
| Neck Diameter | 288 thousandths in | 7 mm and 32 hundredths |
| Shoulder Angle | 30 degrees | 30 degrees |
| Case Capacity | Approx 52 grains water | 3 cubic cm and 38 hundredths |
| Maximum Average Pressure | 62-thousand psi | 427-5 megapascals |
Why 25 Creedmoor Dimensions Matter
Understanding the specific layout of the 25 Creedmoor helps dictate equipment and building choices:
- Magazine and Action Compatibility:Because the maximum overall length reaches up to 2.825 inches, it is designated as a true short-action cartridge designed to fit seamlessly into standard short-action bottom metal and AICS magazines.
- Barrel Twist Selection: Ensuring a barrel is blanked with the proper 1:7.5-inch twist rate is vital; slower legacy quarter-bore twist rates (such as 1:10) will tumble modern high-BC 130+ grain bullets.
What specific bullet weight or application are you planning to load for this cartridge?