AR Bolt Tail Gauges - AKA Gas Efficiency Gauges

This guide, presented by School of the American Rifle, details how to identify and replace a malformed weld spring in an AR-15 Delta Ring assembly. A misaligned weld spring can cause the gas tube to be pushed off-center, leading to excessive friction or damage to the carrier key and gas tube. Replacing the faulty component ensures proper gas tube alignment and firearm reliability.

This video from School of the American Rifle highlights critical manufacturing defects in AR-15 bolt carrier keys, specifically focusing on rough internal bores. Lead instructor demonstrates how a poorly finished carrier key can cause significant friction, premature wear on components like gas tubes, and operational issues, contrasting a problematic new Colt carrier with a well-functioning older model. The expert emphasizes the importance of a smooth bore for reliable function and longevity of expensive parts.

This video addresses a common issue encountered when using .22 Conversion kits with AR-15 platforms, where manufacturing variances can cause compatibility problems. The "Quarter Trick" is presented as a simple and inexpensive solution to rectify these issues. The video encourages viewers to become CMMG Insiders for updates on new releases and provides links to CMMG's website, Instagram, and Twitter for more information and engagement.

This YouTube video offers practical tips and techniques for polishing stainless steel firearm components. The content focuses on achieving a high-quality finish on gun parts, likely aimed at gunsmiths, hobbyists, and firearm enthusiasts looking to customize or maintain their weapons. The video emphasizes real-world application and likely demonstrates various methods and tools used in the polishing process for stainless steel firearms.

This video demonstrates the cleaning and restoration of a heavily fouled Daniel Defense Bolt Carrier Group (BCG) using the Tactical Elites gun cleaning kit. It covers step-by-step disassembly, thorough scrubbing to remove carbon buildup, and meticulous reassembly. The process highlights the importance of proper firearm maintenance for preserving component integrity and functionality, showcasing the effectiveness of the cleaning kit.

This entry details the unique XR-86 custom rifle, a 1986 build by Wilfred Ellis. It masterfully combines components from an M60 (flash hider), an M14 (gas system), and an AR-15 (trigger, bolt, locking system). The AR-15 trigger is notably rotated 90 degrees, and its bolt is integrated with the M14 gas system, showcasing advanced gunsmithing.

This video details the diagnosis and repair of a feeding issue on a Sons of Liberty Gun Works East India upper receiver. The root cause was identified as a sharp burr on the barrel extension's feed ramp, causing rounds to jam. The solution involved polishing the feed ramps and adding a secondary bevel, replicating Colt's design, which successfully resolved the malfunction.

This video demonstrates the internal mechanics of an AR-15 bolt carrier group using cutaway models. It highlights the importance of internal bore dimensions for gas system efficiency and explains how to diagnose potential issues like gas leaks. The demonstration covers the cycle of operation, critical seals, and common manufacturing defects, offering advanced insights for AR-15 maintenance and troubleshooting.

This video provides a detailed autopsy of a faulty AR-15 Bolt Carrier Group (BCG). The analysis reveals critical manufacturing defects including an undersized bolt tail failing gauges, excessive firing pin protrusion causing pierced primers, an oversized firing pin hole, and an oversized cam pin hole leading to headspace issues. These flaws significantly compromise the BCG's function and reliability.

This video demonstrates a specialized technique for swapping an AR-15 rear takedown pin without full firearm disassembly. It highlights the use of a custom-fabricated tool, often made from a 1/16 inch Allen wrench, to depress the detent. The method allows for efficient pin replacement, particularly useful on rifles with staked castle nuts, by leveraging the old pin to guide the new one into place.