How To Make An AR-15 Fully Automatic

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A semi-automatic assault rifle is a thing of beauty to operate, but you may feel like it is like a beast in a cage and not able to reach its full potential! If you are looking to release the beast in your AR-15 and take it to fully automatic, we have detailed the two best methods to get it done!

Making an AR-15 fully automatic requires setting up your AR-15 build to receive an automatic sear, sourcing the rare and expensive sear, and finally undertaking a large amount of paperwork to legally own a fully automatic weapon. The waiting period for approval can take upwards of 6 months.

There are essentially two ways to get your AR-15 to fire in full auto mode. One method is true fully auto, while the second method simulates full auto very effectively and is a way to own what is pretty much a fully automatic AR-15 without the legal ramifications. Here’s how to get it done!

How To Make An AR-15 Fully Automatic

2 Ways To Make Your Ar-15 Fully Automatic

Firing a rifle on full automatic is an experience that needs to be undertaken to be understood! While most gun owners will admit to feeling the need to have the experience, not many people will modify their own AR-15 to take it to full auto.

There is a reason for this, and we will discuss these issues after delving into the 2 methods to unleash the beast in your AR-15!

Install A Bump-Butt To Get Your Ar-15 To Almost Fully Automatic

One of the easiest methods and least expensive ways of achieving a rate of fire almost like full auto, is to install a bump-butt stock on your AR-15.

A bump-butt stock does not technically make your AR-15 fully automatic, which is why it is permitted in some states.

A bump-butt stock has a locked position for normal semi-automatic fire and an unlocked position for rapid, almost fully automatic fire.

When the bump-butt is in locked mode, the mechanism is locked in position, and the stock cannot slide. When the stock is in this configuration, the rifle will only fire one round with each pull of the trigger.

The stock and trigger mechanism can slide backward and forward when the stock is unlocked. In this position, the recoil of the initial round being fired bumps the buttstock and your hand holding the trigger backward.

This backward motion allows the parts in the receiver to cycle fully for semi-auto fire but pulls the trigger for you when the mechanism slides back. The weapon will continue to fire as long as you hold the trigger down.

This mechanism does not modify the sear or require a fully automatic sear installed in the AR-15. Since the mechanism on the rifle is still that of a semi-auto rifle, the bump-butt is deemed legal in some locations, without additional licensing and paperwork.

The disadvantage of a bump-butt stock is that the movement of the stock decreases the accuracy with which the rifle can be fired. It can be an effective rapid-fire solution but don’t expect the same accuracy as you would get with a truly automatic sear.

Woman Shooting AR-15
by Tac6 Media

Install A Fully Automatic Sear to Make Your AR-15 Truly Full Auto

The only way to get genuine fully automatic fire on an AR-15 is to install a sear on the rifle designed for full-auto fire.

The problematic issue with this method is that these sears are no longer allowed to be manufactured legally, and they must be registered with the authorities. Since the auto sears are no longer being manufactured, they have become scarce and consequently expensive.

The second challenge to achieving this modification is the paperwork and licensing requirements you must fulfill to perform this modification on your AR-15. In many states, this modification is illegal, so even if you can get your hands on an auto sear, the modification you’re your rifle would be against the law.

You must replace additional parts on the AR-15 to allow the auto sear to be fitted. An AR-15 intended for the private market will also need the trigger control group replaced with that of the M-16, which is designed to accommodate the fitment of the auto sear.

The process to convert your AR-15 to fully automatic would be as follows.

  • Check legalities. In many states, owning a fully automatic firearm is illegal. Do your due diligence to find out whether this will affect you or not in your state of residence.
  • Source an auto sear. Before making any other changes to your AR-15, source the auto sear. These are difficult to find and can cost you upwards of $30 000, and the original owner must be willing to part with it.
  • Source the other parts. Once you have a sear sourced, you will need to source the additional parts, such as an M-16 trigger control assembly.
  • Fill out the paperwork. You will need to rill out copious amounts of application forms and comply with all the requirements for owning a fully automatic weapon. You will not be allowed to perform the upgrade on your AR-15 until the application is approved, which can take between 6 to 12 months.
Should You Convert Your AR-15 To Fully Automatic

Should You Convert Your AR-15 To Fully Automatic?

The rapid-fire of a rifle on automatic is inherently inaccurate and generally only has application in combat-type circumstances. It is, therefore, highly unlikely you will find a use for this setting on your AR-15 other than to have some fun sending lead down-range at a fully automatic safe shooting range.

As a result, spending in the region of $40 000 to convert your AR-15 to fully automatic simply to have a bit of fun on the shooting range now and again is a pretty hefty price to pay for entertainment.

The scrutiny you will face from the authorities and the time it will take for your registration to come through are other hurdles that deter many AR-15 owners from going this route for the fully automatic experience.

In most parts of the country, owning a fully automatic firearm is only legal if the rifle is manufactured before 1983, and you qualify in your personal capacity to own such a firearm.

The other method to acquire a fully automatic firearm is to apply for a Federal-Firearm License geared to people who work and make a living in the firearms industry. This can be either as a dealer or as a manufacturer.

However, this method of gaining access to fully automatic weapons is detailed, and you will come under strict scrutiny by the ATF, who examine each application on its merits and whether you qualify depending on your personal status and the laws of the state where you reside.


An AR-15 is an amazing firearm with its original build in semi-auto configuration. Owning this weapon will put you at an advantage over anyone else who does not have one! While taking your AR-15 fully automatic is possible, it is not an undertaking that we would recommend.

The onerous registration requirements paired with the high costs generally make the modification impractical for most people. Rather stick with your AR-15 in semi-auto mode, and you will have a perfectly capable firearm for pretty much any situation you are likely to encounter in civilian life!

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