The .338 Lapua Magnum (often shortened to 338 Lapua) is a powerful, long-range cartridge known for its exceptional accuracy and ballistic performance. Understanding its case dimensions is crucial for reloaders, custom cartridge builders, and anyone working with this impressive round. This guide will delve into the specifics of 338 Lapua case dimensions, exploring their significance and practical applications.
Key Dimensions of the 338 Lapua Case
The 338 Lapua's dimensions are defined by several key measurements, each playing a vital role in its functionality and performance. These dimensions are typically expressed in millimeters (mm) or inches (in). Slight variations might exist between manufacturers, so always refer to the specifications of your specific components.
Overall Length (OAL)
The overall length of the 338 Lapua case is a critical dimension. It dictates the maximum cartridge length that can be safely chambered in a firearm. Exceeding the OAL can lead to malfunctions, damage to the firearm, or even injury.
- Typical OAL: 86-87mm (approximately 3.39-3.43 inches) – This is often the manufacturer specified maximum, but this will vary slightly depending on the specific bullet and seating depth.
Case Length
This measurement refers to the length of the cartridge case itself, excluding the bullet. This is important for determining the amount of powder that can be safely accommodated.
- Typical Case Length: Approximately 71.5mm (2.81 inches)
Base Diameter
The base diameter is the measurement across the bottom of the cartridge case, where it meets the primer pocket. This dimension is critical for ensuring proper seating of the case in the chamber.
- Typical Base Diameter: Approximately 13.5 mm (.53 inch)
Shoulder Diameter
The shoulder diameter is the measurement across the widest part of the shoulder of the cartridge case. This dimension plays a critical role in the case's ability to withstand high pressures and maintain a secure seal in the chamber.
- Typical Shoulder Diameter: Approximately 15.1 mm (.59 inch)
Neck Diameter
The neck diameter is the measurement across the narrowest part of the case, where the bullet is seated. This dimension is crucial for ensuring proper bullet fit and preventing bullet setback.
- Typical Neck Diameter: Approximately 9.7 mm (.38 inch)
Understanding the Significance of these Dimensions
Precise dimensions are critical for the proper functioning of the 338 Lapua Magnum cartridge. Incorrect dimensions can lead to several issues:
- Improper Chambering: Incorrect case length or base diameter can prevent the cartridge from fully seating in the chamber, causing malfunctions.
- High Pressure: Case dimensions impact the ability of the cartridge to withstand high pressures generated during firing. Incorrect dimensions can cause dangerously high pressures.
- Bullet Setback: Incorrect neck diameter can result in bullet setback, affecting accuracy and potentially causing dangerous pressure spikes.
- Reloading Problems: Accurate case dimensions are crucial for consistent and reliable reloading.
Case Dimensions and Reloading
For those reloading 338 Lapua, meticulous attention to case dimensions is essential. Using improperly sized cases can lead to serious problems, including:
- Case Head Separation: Using cases with excessive headspace or weak neck walls can lead to case head separation, a potentially catastrophic failure.
- Inconsistent Performance: Inconsistent case dimensions lead to variations in pressure and accuracy, making it difficult to achieve optimal performance.
- Damaged Equipment: Cases with incorrect dimensions can damage reloading dies and other equipment.
It's highly recommended to use precision reloading equipment and carefully check case dimensions before reloading. Caliper measurements are crucial for assessing dimensions to ensure accuracy.
Table of 338 Lapua Magnum Case Dimensions
| Dimension | Metric (mm) | Imperial (in) |
|---|---|---|
| Overall Length (OAL) | 86-87 | 3.39-3.43 |
| Case Length | ~71.5 | ~2.81 |
| Base Diameter | ~13.5 | ~0.53 |
| Shoulder Diameter | ~15.1 | ~0.59 |
| Neck Diameter | ~9.7 | ~0.38 |
Disclaimer: The dimensions provided are typical values and may vary slightly depending on the manufacturer. Always consult the specifications provided by the manufacturer of your specific components. Reloading ammunition can be dangerous. Proceed with caution and follow all safety procedures.