Knights Armament Company SR-15 Lower Receiver - Oversize Bolt Catch Pin Bore & Takedown Bores

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 YouTube video focuses on a common and crucial aspect of firearm ownership: the buffer system. The title, "What buffer system do you use?", directly asks for viewer input on their preferred buffer systems. While the description is empty, the title alone indicates a discussion or inquiry into different buffer systems, which are vital components for the reliable operation of firearms, particularly semi-automatic rifles like the AR-15 platform. Viewers interested in firearm maintenance, customization, or performance optimization would find this content relevant.

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 from AT3 Tactical explores the function and necessity of the forward assist on AR-15 style firearms. It delves into the component's historical origins, specifically its introduction during the Vietnam War era, and examines its practical applications and potential drawbacks on modern rifles. The content aims to educate viewers, whether they are new to building or modifying AR-15s, to make an informed decision about the forward assist's role in their firearm setup. The video also touches on specific drills and potential problems associated with the component.

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 guide details the installation of an aftermarket AR-15 trigger, specifically a Timney Triggers product. The process involves unboxing the trigger, identifying its modular components like interchangeable shoes, and then carefully installing it into a lower receiver. A function test is crucial to confirm correct operation. The speaker demonstrates proficiency with firearm components and installation procedures.

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.