The seemingly insignificant roll pin plays a crucial role in the functionality and safety of your AR-15. Understanding AR-15 roll pin sizes is essential for proper assembly, maintenance, and repairs. This guide provides a detailed breakdown of common roll pin sizes used in various AR-15 components, along with tips for identification and selection.
Common AR-15 Roll Pin Sizes and Their Applications
AR-15 roll pins come in various diameters and lengths, each designed for specific applications. Incorrect sizing can lead to loose components, malfunction, and even potential injury. Here's a breakdown of some of the most frequently encountered sizes:
Note: Measurements are typically given in inches. Always double-check measurements before purchasing or using roll pins.
1/16" Diameter Roll Pins:
These are among the smallest roll pins used in AR-15s and are frequently found in:
- Small parts: These might include certain components within the trigger group or other small internal parts. Precise location varies by manufacturer and specific model.
5/64" Diameter Roll Pins:
A more common size, 5/64" diameter roll pins are used in a wider array of applications, including:
- Trigger pins: These are crucial for holding the trigger and hammer in place. Ensure you use the correct length and diameter to maintain proper trigger function and safety.
- Hammer pins: Similar to trigger pins, hammer pins use this size to secure the hammer within the receiver. Again, accurate sizing is vital for reliable operation.
- Bolt catch pins: This pin secures the bolt catch mechanism, responsible for holding the bolt to the rear after the last round is fired.
3/32" Diameter Roll Pins:
These are slightly larger and used in more robust components:
- Take-down pins: These pins are arguably the most commonly replaced roll pins on an AR-15. They secure the upper and lower receivers together. Incorrect size here can compromise the structural integrity of the rifle.
- Other structural components: Some manufacturers might use this size in other internal parts depending on design and manufacturing specifics.
Identifying and Selecting the Right Roll Pins
Accurately identifying the required roll pin size is critical. Here's how:
- Measure existing pins: The most reliable method is to carefully measure the diameter and length of the existing roll pin using calipers or a precise measuring tool. Note that measuring the hole itself isn't always reliable due to potential wear or manufacturing tolerances.
- Consult diagrams: Detailed exploded diagrams of your specific AR-15 model are readily available online and in manuals. These diagrams often specify the exact roll pin dimensions for each component.
- Use a reputable parts supplier: When ordering replacement parts, ensure you’re using a trusted supplier known for accurate product descriptions and quality control. Purchasing the wrong size can prove costly and time-consuming to rectify.
Beyond Size: Material and Quality
While size is paramount, the material and quality of the roll pin are also important factors. Most AR-15 roll pins are made from hardened steel for durability and resistance to wear. Avoid using cheap or low-quality roll pins, as they can easily bend or break under stress, leading to potential firearm malfunctions.
Conclusion
Understanding AR-15 roll pin sizes is crucial for maintaining a safe and functional firearm. By accurately identifying the correct dimensions and using high-quality roll pins, you can ensure the reliability and longevity of your AR-15. Always prioritize safety and consult with experienced gunsmiths if you have any doubts or are uncomfortable performing maintenance or repairs yourself. Remember, improper handling of firearms can be dangerous.
