# How Does an Auto Sear Work AR15: A Comprehensive Guide to Function, Legality, and Alternatives
Understanding the mechanics of an auto sear in an AR15 is crucial for any firearms enthusiast or professional. This device, designed to convert a semi-automatic AR15 into a fully automatic weapon, is surrounded by legal complexities and technical nuances. This comprehensive guide will delve into the intricate workings of an auto sear, exploring its function, legality, and available alternatives. We aim to provide a clear, authoritative, and trustworthy resource, grounded in expertise and practical understanding, to answer the question: How does an auto sear work AR15?
**What You’ll Learn:**
* The precise mechanism of an auto sear and how it interacts with the AR15’s fire control group.
* The legal ramifications of owning or modifying an AR15 with an auto sear.
* Available alternatives for achieving faster firing rates without violating the law.
* Common misconceptions and safety considerations related to auto sears.
This guide is designed to provide you with a thorough understanding of auto sears in AR15s, empowering you to make informed decisions and stay within the bounds of the law.
## Understanding the Auto Sear AR15 Mechanism: A Deep Dive
The auto sear, at its core, is a small, often unassuming component that dramatically alters the firing characteristics of an AR15 rifle. To fully grasp how does an auto sear work AR15, we must first understand the standard semi-automatic operation of the rifle.
### Semi-Automatic vs. Automatic: The Fundamental Difference
In a semi-automatic AR15, one trigger pull results in a single shot fired. The firing cycle involves:
1. Pulling the trigger.
2. The hammer falls, striking the firing pin.
3. The cartridge ignites, propelling the bullet.
4. Gas from the fired cartridge cycles the bolt carrier group (BCG) rearward.
5. The BCG extracts and ejects the spent casing.
6. The BCG cocks the hammer.
7. The BCG returns forward, stripping a new cartridge from the magazine and chambering it.
8. The rifle is ready to fire again, but the trigger must be released and pulled again.
An automatic weapon, conversely, continues to fire as long as the trigger is depressed and ammunition is available. This continuous firing is achieved by eliminating the need to release the trigger between each shot. This is where the auto sear comes into play.
### How Does an Auto Sear Work AR15: The Technical Explanation
The auto sear replaces or supplements the existing sear in the AR15 fire control group. Its primary function is to intercept and release the hammer at the precise moment required for fully automatic fire. Here’s a simplified breakdown:
1. **Trigger Pull:** When the trigger is pulled and held down, the auto sear, instead of the standard sear, holds the hammer back after the first shot.
2. **Bolt Carrier Group (BCG) Interaction:** As the BCG cycles rearward during the firing cycle, it interacts with the auto sear. This interaction releases the hammer.
3. **Continuous Fire:** The hammer falls, firing another round. This cycle repeats as long as the trigger is held down and ammunition is available.
The crucial difference is that the auto sear bypasses the disconnector, a component in the standard AR15 that prevents the hammer from following the bolt carrier forward when the trigger is held down. The auto sear allows the hammer to follow the bolt carrier, resulting in continuous fire.
### Key Components and Their Roles
* **The Auto Sear:** The central component, responsible for timing the release of the hammer.
* **The Hammer:** Strikes the firing pin to ignite the cartridge.
* **The Bolt Carrier Group (BCG):** Its movement triggers the auto sear.
* **The Disconnector:** Bypassed by the auto sear to allow continuous fire.
### Understanding the Timing
The precise timing of the auto sear is critical. If the hammer is released too early or too late, the weapon may malfunction or fail to fire. This timing is determined by the design and tolerances of the auto sear and its interaction with the BCG.
### The Evolution of Auto Sear Designs
Over time, various auto sear designs have emerged, each with its own advantages and disadvantages. Some common designs include:
* **Drop-in Auto Sears (DIAS):** Self-contained units that can be installed in some AR15 lowers with minimal modification. These are particularly scrutinized by law enforcement due to their ease of installation.
* **Lightning Links:** A less common type of conversion device, similar in function to an auto sear.
## The Legal Landscape of Auto Sears: Navigating the NFA
The legal status of auto sears is complex and heavily regulated by the National Firearms Act (NFA) of 1934 and subsequent amendments. Understanding these regulations is paramount for any AR15 owner.
### The National Firearms Act (NFA) and Definition of Machine Guns
The NFA defines a machine gun as any weapon that can fire multiple shots with a single pull of the trigger. This definition encompasses firearms equipped with auto sears, classifying them as machine guns. Machine guns are heavily restricted under federal law.
### Restrictions and Requirements
Owning a legally registered machine gun is possible in some states, but it requires:
* **Federal Registration:** The firearm must be registered with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).
* **Background Checks:** Extensive background checks are required.
* **Tax Stamps:** A transfer tax must be paid for each transfer of ownership.
* **State and Local Laws:** Compliance with state and local laws, which may prohibit machine gun ownership entirely.
### The Stiff Penalties for Illegal Possession
Possessing an unregistered auto sear or a modified AR15 that functions as a machine gun carries severe penalties, including:
* **Federal Prison:** Up to 10 years in federal prison.
* **Significant Fines:** Substantial fines.
* **Forfeiture:** Forfeiture of the firearm and any related property.
### The ATF’s Scrutiny
The ATF closely monitors the sale and possession of auto sears and conversion devices. Even the possession of an auto sear without a registered firearm can be considered a violation of the NFA, if the ATF can prove intent to manufacture a machine gun.
### Landmark Cases and Legal Interpretations
Several court cases have shaped the legal interpretation of auto sears and the NFA. These cases often revolve around the definition of a “machine gun” and the intent of the possessor.
## Alternatives to Auto Sears: Achieving Faster Firing Rates Legally
While the allure of fully automatic fire is undeniable, it’s crucial to explore legal alternatives that can enhance the firing rate of an AR15 without running afoul of the NFA.
### Bump Stocks: A Controversial Option (Currently Restricted)
Bump stocks were designed to allow a semi-automatic rifle to simulate automatic fire by harnessing recoil energy. However, the ATF has since classified bump stocks as machine guns, effectively banning their sale and possession. Note: Legal challenges to this classification are ongoing, but as of now, bump stocks are largely illegal.
### Binary Triggers: A Popular and Legal Choice
Binary triggers are a popular alternative that allows the rifle to fire both when the trigger is pulled and when it is released. This effectively doubles the rate of fire compared to a standard semi-automatic trigger.
#### How Binary Triggers Work
Binary triggers have two modes:
1. **Semi-Automatic Mode:** Functions like a standard AR15 trigger (one shot per trigger pull).
2. **Binary Mode:** Fires one round when the trigger is pulled and another round when the trigger is released.
#### Legal Considerations for Binary Triggers
Binary triggers are generally legal at the federal level, but it’s essential to check state and local laws, as some jurisdictions may restrict or prohibit their use.
### FRT Triggers (Forced Reset Triggers):
FRT triggers are designed to force the trigger to reset faster than a standard trigger, allowing for a rapid rate of fire. These are more expensive than binary triggers, but are also more effective at increasing the rate of fire.
### Trigger Modifications: Proceed with Caution
Modifying the existing trigger mechanism of an AR15 to increase the firing rate can be risky, both legally and mechanically. Any modification that results in the rifle firing more than one shot per trigger pull is likely to be considered a violation of the NFA.
## Auto Sear AR15: Dispelling Common Misconceptions
Numerous misconceptions surround auto sears and their use in AR15s. Let’s address some of the most prevalent ones:
### Misconception 1: “Auto Sears are Easy to Install”
While some auto sears, like DIAS, can be installed relatively easily, proper installation requires a degree of technical skill. Improper installation can lead to malfunctions or even damage to the firearm.
### Misconception 2: “Owning an Auto Sear is No Big Deal if You Don’t Use It”
As mentioned earlier, the mere possession of an auto sear can be a federal offense if the ATF can demonstrate intent to use it to convert a semi-automatic rifle into a machine gun.
### Misconception 3: “All AR15s Can Be Easily Converted to Full Auto”
While the AR15 platform is adaptable, not all AR15s are easily converted to full auto. Some models require extensive modifications that are beyond the capabilities of the average gun owner.
### Misconception 4: “Bump Stocks are the Same as Auto Sears”
While both devices can increase the firing rate of a semi-automatic rifle, they operate on different principles. Auto sears directly modify the fire control group, while bump stocks harness recoil energy.
## The Importance of Safety and Responsible Gun Ownership
Regardless of your interest in auto sears or alternative firing mechanisms, safety should always be the top priority. Responsible gun ownership includes:
* **Safe Handling:** Always handle firearms with care and follow established safety rules.
* **Proper Storage:** Store firearms securely to prevent unauthorized access.
* **Legal Compliance:** Stay informed about and comply with all applicable federal, state, and local laws.
* **Training:** Seek professional training in firearms safety and handling.
## Q&A: Expert Answers to Your Auto Sear AR15 Questions
Here are 10 frequently asked questions about auto sears and AR15s, answered with expert insights:
1. **Q: Can I legally manufacture my own auto sear if I have a registered machine gun?**
**A:** Manufacturing an auto sear, even for a registered machine gun, may require specific ATF approvals. It’s crucial to consult with the ATF and understand the regulations before attempting to manufacture any NFA-regulated item.
2. **Q: What are the key differences between a DIAS and a registered receiver?**
**A:** A DIAS (Drop-In Auto Sear) is a separate device that converts a semi-automatic AR15 into a machine gun. A registered receiver is a complete AR15 lower receiver that has been registered as a machine gun. The DIAS can potentially be used in multiple hosts, while the registered receiver is tied to that specific lower receiver.
3. **Q: If I find an old auto sear in my grandfather’s belongings, what should I do?**
**A:** Immediately contact the ATF. Possessing an unregistered auto sear is a federal offense, even if you were unaware of its existence. The ATF can advise you on how to properly dispose of or register the device.
4. **Q: Are there any states where auto sears are legal without federal registration?**
**A:** No. Federal law requires all machine guns, including those created with auto sears, to be registered with the ATF, regardless of state laws. State laws can further restrict or prohibit machine gun ownership, even with federal registration.
5. **Q: What are the chances of being prosecuted for owning an auto sear if I never install it in a firearm?**
**A:** The risk of prosecution depends on the ATF’s ability to prove intent to manufacture a machine gun. Possessing an auto sear along with AR15 parts and instructions on how to convert it increases the risk.
6. **Q: How does the ATF determine if a device is an auto sear or just a modified AR15 part?**
**A:** The ATF uses its technical expertise to examine the device and determine its function. If the device is designed to convert a semi-automatic rifle into a machine gun, it will likely be classified as an auto sear.
7. **Q: What are some red flags that might attract the ATF’s attention regarding auto sears?**
**A:** Purchasing multiple AR15 parts, including fire control components, without a legitimate reason, searching online for information about auto sear installation, and discussing auto sear conversions with others can all raise red flags.
8. **Q: Can I legally own a deactivated auto sear as a historical artifact?**
**A:** Even a deactivated auto sear may be subject to NFA regulations. It’s best to consult with the ATF to determine the legal status of a deactivated auto sear before acquiring one.
9. **Q: What is the difference between a burst trigger and an auto sear?**
**A:** A burst trigger allows the firearm to fire a limited number of rounds (typically 3) with a single trigger pull, whereas an auto sear allows for continuous fire as long as the trigger is depressed.
10. **Q: Are there any legal AR-15 platforms that operate nearly identically to full-auto rifles?**
**A:** No AR-15 platform operates *identically* to a full-auto rifle without violating NFA regulations. While some triggers, like FRT triggers, can produce very high rates of fire, they are still considered semi-automatic under the law because they fire only one shot per function of the trigger.
## Conclusion: Navigating the Complex World of Auto Sears and AR15s
Understanding how does an auto sear work AR15 is just the first step. The legal and ethical considerations surrounding these devices are equally important. By staying informed, adhering to the law, and prioritizing safety, you can navigate the complex world of AR15s responsibly. Remember that this guide is for informational purposes only and does not constitute legal advice. Always consult with a qualified attorney or firearms expert for specific guidance.
We hope this comprehensive guide has provided you with a deeper understanding of auto sears and their role in AR15s. Share your thoughts and experiences in the comments below, and explore our other resources for more information on firearms safety and responsible gun ownership. Contact our experts for a consultation on AR-15 builds and legal compliance.
