The .308 Winchester is one of the most widely used rifle cartridges in the world, and understanding the exact 308 cartridge dimensions is essential for both technical reference and practical application. The key measurements include a nominal bullet diameter of 0.308 inches, a maximum case length of 2.015 inches, and a maximum overall cartridge length of 2.810 inches. Published dimensions can vary slightly depending on whether the specification comes from the Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) or the Commission Internationale Permanente pour l’Epreuve des Armes à Feu Portatives (C.I.P.).
308 Cartridge Dimensions
| Dimension | Inches | Millimeters | Specification |
| Bullet Diameter | 0.3090 | 7.85 | SAAMI Maximum |
| Case Length | 2.015 | 51.18 | SAAMI / C.I.P. Maximum |
| Overall Cartridge Length | 2.810 | 71.37 | SAAMI Maximum |
| Rim Diameter | 0.4728 | 12.01 | SAAMI Maximum |
| Base Diameter | 0.4709 | 11.96 | SAAMI Maximum |
| Shoulder Diameter | 0.4539 | 11.53 | SAAMI Maximum |
| Neck Diameter | 0.3433 | 8.72 | SAAMI Maximum |
| Rim Thickness | 0.0539 | 1.37 | SAAMI Maximum |
| Shoulder Angle | 20 degrees | 20 degrees | SAAMI / C.I.P. Reference |
308 Cartridge Dimensions: The .308 Winchester has a maximum case length of 2.015 inches (51.18 mm), with a maximum SAAMI overall cartridge length of 2.810 inches (71.37 mm) and a nominal bullet diameter of .308 inches (7.82 mm).
What Are the Dimensions of a 308 Cartridge?
The physical measurements of the .308 Winchester dictate how the ammunition interacts with the firearm.
Bullet diameter represents the outer width of the projectile where it engages the rifling of the barrel. Case length is the distance from the base of the brass case to its mouth. Overall cartridge length measures the total distance from the case head to the tip of the seated bullet. Rim diameter measures the width of the extractor flange at the base of the cartridge. Base diameter is the width of the cartridge body just ahead of the extractor groove. Shoulder diameter measures the width of the cartridge body just before it angles inward. Neck diameter is the outside width of the case mouth that physically holds the bullet in place. Rim thickness is the depth of the rim from the base face to the extractor groove, which dictates headspace in some firearm actions. Finally, the shoulder angle is the slope of the brass where the main body transitions to the narrower neck.
308 Cartridge Dimensions in Inches and Millimeters
| Dimension | Inches | Millimeters |
| Bullet diameter | 0.3090 | 7.85 |
| Case length | 2.0150 | 51.18 |
| Overall length | 2.8100 | 71.37 |
| Rim diameter | 0.4728 | 12.01 |
| Base diameter | 0.4709 | 11.96 |
| Shoulder diameter | 0.4539 | 11.53 |
| Neck diameter | 0.3433 | 8.72 |
| Rim thickness | 0.0539 | 1.37 |
308 Case Dimensions
| Case Dimension | Inches | Millimeters |
| Maximum case length | 2.015 | 51.18 |
| Rim diameter | 0.4728 | 12.01 |
| Rim thickness | 0.0539 | 1.37 |
| Base diameter | 0.4709 | 11.96 |
| Shoulder diameter | 0.4539 | 11.53 |
| Neck diameter | 0.3433 | 8.72 |
| Shoulder angle | 20 degrees | 20 degrees |
Case dimensions refer exclusively to the brass housing, while cartridge dimensions include the seated projectile. The C.I.P. standard defines the maximum overall length as 2.800 inches (71.12 mm), whereas SAAMI lists a maximum overall length of 2.810 inches (71.37 mm). However, the underlying brass casing dimensions are virtually identical between the two governing bodies.
308 Cartridge Overall Length
Cartridge overall length is defined by SAAMI as the greatest dimension of a loaded cartridge measured from the head of the casing to the tip of the bullet. This standardized maximum dimension remains important for cartridge specifications because it ensures the loaded ammunition will physically fit inside standardized rifle magazines and cycle properly through firearm actions.
Overall length can vary significantly depending on bullet design and seating position. Long, aerodynamic bullets with heavy tapers might be seated deeper or shallower than blunt hunting projectiles, altering the total length of the physical cartridge while remaining within the SAAMI maximum of 2.810 inches.
308 Bullet Dimensions
Bullet dimensions are measured separately from the complete cartridge. The .308 Winchester uses a nominal bullet diameter of 0.308 inches, with maximum manufacturing tolerances usually allowing up to 0.3090 inches. Bullet weight ranges drastically based on the intended application, while bullet length varies between individual bullet designs even when bullet diameter and weight remain identical. Different bullet profiles create different ballistic coefficients, altering how the projectile performs in flight.
| Common .308 Winchester Bullet Weights |
| 110 grain |
| 125 grain |
| 150 grain |
| 155 grain |
| 165 grain |
| 168 grain |
| 175 grain |
| 180 grain |
| 190 grain |
| 200 grain |
| 220 grain |
308 Cartridge Dimensions vs 7.62 NATO
| Dimension | .308 Winchester | 7.62×51mm NATO |
| Bullet diameter | 0.3090 in (7.85 mm) | 0.3090 in (7.85 mm) |
| Case length | 2.015 in (51.18 mm) | 2.015 in (51.18 mm) |
| Overall cartridge length | 2.810 in (71.37 mm) | 2.750 in (69.85 mm) typical |
| Rim diameter | 0.4728 in (12.01 mm) | 0.4728 in (12.01 mm) |
| Base diameter | 0.4709 in (11.96 mm) | 0.4709 in (11.96 mm) |
| Shoulder dimensions | 0.4539 in (11.53 mm) | 0.4539 in (11.53 mm) |
| Neck dimensions | 0.3433 in (8.72 mm) | 0.3450 in (8.76 mm) typical |
The .308 Winchester and 7.62×51mm NATO are closely related and share nearly identical exterior physical profiles. However, they should not simply be treated as identical specifications in every respect. Military 7.62 NATO casings are often manufactured with thicker brass walls to withstand specific military extraction processes, which reduces internal case capacity compared to commercial .308 Winchester brass. Furthermore, military chambers are often cut slightly longer to guarantee feeding under harsh conditions.
308 Cartridge Dimensions vs 30 06
| Dimension | .308 Winchester | .30-06 Springfield |
| Bullet diameter | 0.308 in (7.82 mm) | 0.308 in (7.82 mm) |
| Case length | 2.015 in (51.18 mm) | 2.494 in (63.35 mm) |
| Overall cartridge length | 2.810 in (71.37 mm) | 3.340 in (84.84 mm) |
| Rim diameter | 0.4728 in (12.01 mm) | 0.4730 in (12.01 mm) |
| Base diameter | 0.4709 in (11.96 mm) | 0.4710 in (11.96 mm) |
| Typical bullet weights | 150 to 180 grain | 150 to 220 grain |
The .308 Winchester was directly developed to replicate the ballistic performance of the older .30-06 Springfield while utilizing a much shorter case. While both cartridges use identical bullet diameters and nearly identical rim and base dimensions, the .30-06 Springfield features a significantly longer case and overall cartridge length. The increased case capacity of the .30-06 allows it to push heavier bullets more efficiently.
308 Cartridge Dimensions vs 223
The size difference between the .308 Winchester and the .223 Remington is substantial. The .308 Winchester utilizes a .308 inch bullet diameter, while the .223 Remington utilizes a much smaller .224 inch bullet. The .308 Winchester has a maximum case length of 2.015 inches and an overall length of 2.810 inches. In contrast, the .223 Remington is much shorter with a maximum case length of 1.760 inches and an overall length of 2.260 inches. The .308 base diameter (0.4709 inches) and rim diameter (0.4728 inches) are vastly wider than the .223 Remington base (0.3769 inches) and rim (0.3780 inches). Typical .308 bullet weights span 150 to 180 grains, heavily outweighing the 55 to 77 grain bullets common in .223 Remington.
308 Cartridge Dimensions vs 6.5 Creedmoor
| Dimension | .308 Winchester | 6.5 Creedmoor |
| Bullet diameter | 0.308 in (7.82 mm) | 0.264 in (6.71 mm) |
| Case length | 2.015 in (51.18 mm) | 1.920 in (48.77 mm) |
| Overall cartridge length | 2.810 in (71.37 mm) | 2.825 in (71.76 mm) |
| Base diameter | 0.4709 in (11.96 mm) | 0.4700 in (11.94 mm) |
| Rim diameter | 0.4728 in (12.01 mm) | 0.4730 in (12.01 mm) |
| Shoulder angle | 20 degrees | 30 degrees |
The 6.5 Creedmoor is built around a modified .308-family cartridge case, but features a shorter case length and a sharper shoulder angle to allow for the seating of long, aerodynamic 6.5mm bullets without exceeding standard magazine lengths.
308 Cartridge Size and Rifle Compatibility
Cartridge dimensions are critically important for proper firearm chambering and ammunition identification. Chambers are cut to specific dimensions, and attempting to fire incorrectly sized ammunition can result in catastrophic failure. Ammunition must exclusively match the cartridge designation specified by the firearm manufacturer on the barrel stamping.
308 Cartridge Dimensions and Pressure
Cartridge dimensions govern the physical size, while pressure specifications govern the internal power. SAAMI lists a maximum average pressure of 62,000 psi for the .308 Winchester measured via conformal piezo transducer. The C.I.P. maximum pressure specification is listed at 415.00 MPa (approximately 60,191 psi) measured by their own testing methodology. SAAMI and C.I.P. pressure measurements are not directly interchangeable because the testing bodies measure pressure at different locations within the test barrels.
308 Cartridge Dimensions FAQs
What are the dimensions of a 308 cartridge?
The .308 Winchester features a maximum case length of 2.015 inches, an overall maximum length of 2.810 inches, and a nominal bullet diameter of 0.308 inches.
What is the length of a 308 cartridge?
The maximum SAAMI overall cartridge length of a fully loaded .308 Winchester is 2.810 inches (71.37 mm).
How long is a 308 case?
The maximum published case length for the .308 Winchester brass casing is 2.015 inches (51.18 mm).
What is the diameter of a 308 cartridge?
The widest point of the main cartridge body is the base diameter, which measures a maximum of 0.4709 inches (11.96 mm).
What is the diameter of a 308 bullet?
The nominal bullet diameter for the .308 Winchester is 0.308 inches (7.82 mm).
What is the overall length of a 308 cartridge?
The SAAMI maximum overall length is 2.810 inches, while the C.I.P. maximum overall length is 2.800 inches.
What is the maximum case length of 308 Winchester?
The official maximum case length is 2.015 inches (51.18 mm).
What is the rim diameter of a 308?
The maximum rim diameter measures 0.4728 inches (12.01 mm).
What is the base diameter of a 308?
The maximum base diameter ahead of the extractor groove is 0.4709 inches (11.96 mm).
What is the shoulder diameter of a 308?
The maximum shoulder diameter measures 0.4539 inches (11.53 mm).
What is the neck diameter of a 308?
The maximum neck diameter is 0.3433 inches (8.72 mm).
Is 308 the same size as 7.62 NATO?
They share nearly identical exterior physical dimensions, but 7.62 NATO casings typically feature thicker brass walls, and the firearms utilize slightly different chamber specifications.
Is 308 bigger than 223?
Yes, the .308 Winchester is substantially larger than the .223 Remington in bullet diameter, case length, and overall size.
Is 308 longer than 30 06?
No, the .308 Winchester has a maximum overall length of 2.810 inches, while the .30-06 Springfield is much longer with a maximum overall length of 3.340 inches.