The accuracy of your AR-15 heavily relies on proper barrel alignment within the upper receiver. Even minor misalignment can lead to significant accuracy issues, impacting your shooting performance. This is where AR-15 barrel shims come into play. These small, precisely-machined components are crucial for ensuring your barrel is perfectly centered and aligned, maximizing your rifle's potential. This guide delves into the world of AR-15 barrel shims, explaining their purpose, types, and how to use them effectively.
Understanding the Importance of Barrel Alignment
The AR-15's gas system relies on precise alignment between the barrel and the bolt carrier group. Misalignment can result in:
- Reduced Accuracy: A crooked barrel introduces inconsistencies in bullet trajectory, leading to noticeable dispersion at the target.
- Increased Recoil: Misalignment can cause uneven stress on the receiver, resulting in increased felt recoil and potentially damaging the rifle over time.
- Malfunctions: Severe misalignment can interfere with the gas system's function, leading to jams, failures to feed, or other malfunctions.
Types of AR-15 Barrel Shims
AR-15 barrel shims come in various materials and thicknesses, each designed for specific purposes:
Material:
- Steel: Steel shims are the most common type, offering durability and precision. They are generally preferred for their ability to withstand the stresses of firing.
- Aluminum: Aluminum shims are lighter than steel, but may not be as durable in high-round-count situations. They are sometimes used where weight reduction is paramount.
Thickness:
Shims are typically available in a range of thicknesses, often measured in thousandths of an inch (e.g., 0.010", 0.020", 0.030"). The necessary thickness depends entirely on the specific rifle and the degree of misalignment. You may need to experiment with different thicknesses to achieve perfect alignment.
Identifying the Need for Barrel Shims
Before introducing shims, you need to assess whether your AR-15 barrel requires adjustment. There are a few ways to check:
- Visual Inspection: Carefully examine the barrel's position within the upper receiver. Look for any obvious misalignment or gaps.
- Headspace Gauges: While not directly measuring alignment, proper headspace setup is critical and indirectly indicates barrel fit. If your headspace is off, it often relates to barrel fit issues.
- Test Firing: If you experience consistent accuracy issues, despite properly zeroed optics and ammunition, barrel alignment is a suspect.
How to Install AR-15 Barrel Shims
Installing AR-15 barrel shims requires precision and patience. It's recommended to have the right tools and a steady hand:
- Disassemble the Upper Receiver: Carefully disassemble your upper receiver, removing the barrel nut and handguard.
- Assess the Alignment: Determine which side(s) require shimming based on your assessment of the barrel's position.
- Insert Shims: Carefully place the shim(s) into the appropriate position between the barrel extension and the upper receiver.
- Reassemble the Upper Receiver: Tighten the barrel nut to the manufacturer's specified torque.
- Test Fire: After reassembly, test fire your rifle to verify that the shims have corrected the alignment.
Choosing the Right Shims: A Practical Approach
Determining the precise shim thickness often requires trial and error. Starting with thinner shims and progressively increasing thickness is the safest approach. It’s essential to frequently check the barrel's alignment throughout the process.
Conclusion: Precision through Proper Alignment
AR-15 barrel shims are often overlooked but play a critical role in achieving optimal accuracy and reliability. By understanding their purpose and following the correct installation procedures, you can significantly enhance the performance of your AR-15. Remember that safety is paramount; if unsure, consult a qualified gunsmith.
