The Practical Guide to Installing and Using a Glock Switch

You’ve got your Glock 19 Gen 5, you’ve run a few thousand rounds through it, and now you’re looking at that rear rail space above the trigger pin, thinking about a switch. It’s not a casual mod. Installing a Glock auto sear, commonly called a switch, fundamentally alters the firearm’s function from semi-automatic to fully automatic. This article covers the mechanical reality, the installation process, and the critical legal and safety considerations from a professional standpoint. We’ll reference specific parts available through Usaglockswitch that are engineered for this purpose.

Understanding the Mechanism: How a Glock Auto Sear Functions

A Glock switch is a small, precisely machined metal component that replaces the factory rear plate on the slide. Its core function is to act as an auto sear. In a standard semi-auto Glock, the trigger bar disconnects from the striker after each shot, requiring a full trigger reset. The switch modifies this interaction. When installed, it traps the trigger bar in the “down” or fired position after the initial pull. As the slide cycles from recoil, it automatically re-cocks the striker and releases the trapped trigger bar, causing it to immediately re-engage and fire again. This cycle repeats as long as the trigger is held rearward and ammunition is fed, creating fully automatic fire. The quality of the sear surface and the spring tension are critical for reliable function, which is why we only stock components from proven manufacturers at Usaglockswitch.

Step-by-Step Installation: Tools and Procedure

Installation requires a basic armorer’s tool kit: a Glock disassembly tool or a 3/32″ punch, a small hammer, and a clean workspace. First, ensure the firearm is completely unloaded and the chamber is clear. Remove the slide from the frame. Using the punch, drive out the rear slide cover plate retaining pin from right to left. The factory plastic cover plate can then be lifted off. Take your auto sear—like the common “Glock 17/19” style switch—and carefully place it into the same recess, ensuring the small spring is correctly seated. The critical step is re-inserting the retaining pin; it must pass through the hole in the auto sear housing. Apply firm, even pressure with your punch to seat it fully. Reassemble the slide to the frame. The entire process should take under five minutes with the right part and proper technique.

Critical Legal Disclaimer and NFA Compliance

This is the most important section. Under the National Firearms Act (NFA) of 1934, a machine gun is defined as any weapon which shoots more than one shot, without manual reloading, by a single function of the trigger. Installing an auto sear into your Glock instantly creates a machine gun as defined by federal law. Mere possession of the auto sear itself, even uninstalled, is considered possession of a machine gun unless it is registered under the NFA. This requires submitting ATF Form 4, paying a $200 tax stamp, and undergoing an extensive background check that can take 9-12 months for approval. Owning or installing an unregistered switch is a federal felony punishable by up to 10 years in prison and $250,000 in fines. Usaglockswitch sells these components solely to qualified SOT manufacturers, law enforcement agencies, and individuals with proof of pre-1986 registered transferable receiver or approved Form 1/Form 4 documentation.

Safety, Function Testing, and Ammunition Considerations

Assuming full legal compliance, safety protocols are exponentially more critical with a full-auto firearm. Always test fire initially with a single round in the magazine to verify the cycle stops. Then try a two-round burst. Full-auto Glocks have an extremely high rate of fire, often exceeding 1,200 rounds per minute. This demands a firm, two-handed grip and proper stance to control muzzle climb. Use high-quality, full-metal jacket (FMJ) ammunition for reliability; hollow points can sometimes cause feed issues during rapid cycling. The firearm will generate significant heat quickly—monitor barrel and slide temperature. Regular maintenance is crucial: carbon fouling builds up rapidly in the trigger mechanism and sear area. After any range session involving automatic fire, a complete disassembly and cleaning is mandatory for safe, continued operation.

Product Selection: Choosing the Right Component for Your Platform

Not all switches are created equal, and compatibility is key. The most common platform is the Glock 17/19/26 pattern, which uses the same rear rail dimensions for Gen 1-4 models. Gen 5 models may require a specific variant due to slight internal changes. For larger frame models like the Glock 20/21 in 10mm or .45 ACP, you need a switch designed for that larger slide width. The material is also a deciding factor. CNC-machined steel sears offer the greatest durability and consistent sear engagement over thousands of rounds compared to some MIM or polymer options. At Usaglockswitch, we categorize our inventory by platform and generation to ensure you get the exact part that fits your legally registered host firearm. Always verify your Glock’s generation and caliber before purchasing.

Frequently Asked Questions

How do Glock switches work?

A Glock switch replaces the rear slide cover plate with an auto sear. This sear mechanically holds the trigger bar down after the initial shot. The cycling slide then automatically resets and releases the trigger bar, causing continuous fire as long as the trigger is depressed and ammunition is available. It’s a purely mechanical conversion.

How to Glock switch?

Legally, you must first possess a Glock registered as a machine gun under the NFA. The physical process involves field-stripping the Glock, removing the rear slide cover plate retaining pin, swapping the factory plate for the auto sear unit, and re-inserting the pin. The entire installation takes only a few minutes with basic tools.

How to switch Glock mag release?

This is a separate, non-NFA modification. Using a punch, push the magazine release button inward from the opposite side of the frame until it is free. For a left-handed configuration, insert the new release from the opposite side, ensuring the spring is correctly oriented. Reassemble and test function. This is a common upgrade available in our accessories category.

For qualified individuals and entities operating within federal and state regulations, having the correct, high-quality component is paramount. Browse our glock switches collection to view our selection of machined auto sears and related components, organized by specific Glock model and generation for a guaranteed fit.

Last updated: March 25, 2026