AR-15 Auto Sear- What You Need to Know

What Is an AR-15 Auto Sear?

An AR-15 auto sear is a small device that converts a semi-automatic AR-15 rifle into a fully automatic machine gun.

It works by replacing the standard trigger sear in the lower receiver. The device hooks onto the hammer and releases it continuously as long as you hold the trigger down.

These are also called "drop-in sears" or "lightning links" depending on the design. Both terms refer to the same thing: a part that turns legal firearms into illegal machine guns.

Legal Status: This Is Where It Gets Serious

Under federal law, an auto sear is a machine gun. Full stop.

The Gun Control Act of 1968 and the National Firearms Act define machine guns as any device that converts a firearm to fire automatically. The 1986 Firearms Owners' Protection Act reinforced this.

You cannot legally own one unless it was registered before May 19, 1986. That's the hard cutoff date. Any auto sear manufactured after that date is contraband—period.

The Hughes Amendment

This is the clause that killed civilian machine gun ownership for practical purposes. It was tacked onto the 1986 FOPA and effectively banned the registration of new machine guns after the deadline.

Auto sears fall squarely under this ban. Owning one manufactured after May 1986 is a felony under federal law.

Types of Auto Sears

Not all auto sears are created equal in the eyes of the law:

• Registered pre-86 auto sears — Legal to own if you pass background checks, pay the $200 tax stamp, and live in a state that allows NFA items
• Post-86 auto sears — Illegal to possess, manufacture, or transfer
• Unregistered auto sears — Also illegal, regardless of when they were made

Registration Requirements (If You're One of the Rare Exceptions)

For pre-86 registered auto sears, the process is brutal:

• Submit Form 4 to the ATF
• Pay the $200 tax stamp
• Pass extensive background checks
• Wait 12+ months for approval
• Pass post-approval background check at your local gun store

Even after all that, your auto sear is registered to that specific serial number. Lose it, destroy it, or have it stolen—you're still on the hook.

State Laws: The Layered Problem

Federal law is the floor, not the ceiling. Many states have their own restrictions that make NFA items even harder to own.

Check your state laws before assuming anything. Some states have explicit bans on machine gun possession that supersede federal registration.

Penalties for Illegal Possession

If you get caught with an illegal auto sear, the consequences are severe:

• Up to 10 years in federal prison
• Fine up to $250,000
• Forfeiture of all firearms
• Loss of second amendment rights

Prosecutors don't mess around with machine gun cases. The ATF has dedicated task forces looking for these devices.

What About Parts and "Parts Kits"?

The gray market around auto sear parts is just as dangerous legally. Any component designed exclusively for converting a firearm to automatic fire is treated the same as the complete device.

Buying a "parts kit" thinking you're skirting the law won't save you. If the parts are designed to create a machine gun, they're machine gun parts under the law.

The Bottom Line

For 99.9% of gun owners, auto sears are off-limits. The legal path to ownership is narrow, expensive, and restricted to pre-1986 registered devices that are incredibly rare and expensive.

If you're considering one for any reason, talk to a firearms attorney before you touch anything. The legal exposure isn't worth the risk.