Upgrading Your AR Handguards to a Rail System

By Mark Butler

Written By: Michael Duong

Edited By: Mark Butler

America’s most popular modern sporting rifle, the AR-15, has advanced greatly over the past decade. The era of basic plastic handguards is over. With so many different accessories for ARs available now, handguards that do not offer mounting options just won’t cut it anymore. When rail systems and free-float handguards first hit the market, they were prohibitively expensive and mostly limited to military, law enforcement and competitive users. Today, a great number of manufacturers are making rail systems standard options on their rifles so customers can easily mount things like flashlights, grips and lasers. If your AR does not have one, upgrading is simple. Depending on your skill level and the type of rail purchased, you might even be able to do the work yourself and skip a visit to the gunsmith.

AR-15 is the most popular type of rifle in the world.
An AR-15

Types of Rails

When selecting rails, you generally have the choice between free-float and non-free-float (also known as drop-in) options. Free-float rails do not make contact with the barrel, increasing the rifle’s accuracy due to barrel harmonics. The mounting systems for free-float rails are typically stronger and more rigid as well, but often require tools to install. Drop-in options are much easier to install and usually do not require the use of any tools. Drop-in rails, like Firefield’s Edge Carbine Two-Piece Rail are, a great option for those who need a quick non-free-float upgrade option that enables them to reliably mount accessories.

AR-15 rails systems and hand guards utilize many different designs and patterns.
Firefield Edge Series 7in Keymod Free-float Rail

Rail Patterns and Designs

When it comes to rail designs, there are three main options: Picatinny (also known as MIL-STD-1913 Rail), Keymod and M-LOK. All three are designed to be an interface system for mounting sights, optics and accessories. Picatinny rails are the oldest design of the three. The design was started in the 1980s by companies trying to standardize the Weaver design. Picatinny Arsenal in New Jersey completed and standardized the design in the 1990s. One of the earliest designs featuring a Picatinny rail was the upper receivers on M16 rifles and M4 carbines, giving them an easier option to mount optics. Eventually, the Picatinny rail was incorporated into handguard designs. These Picatinny-railed handguards came to be commonly known as “quad rails.” Although the design is older and heavier than the other options mentioned, Picatinny rails are still very much relevant. They are still in use with the U.S. military and LE agencies nationwide. Most rail manufacturers still produce quad rail options. After Picantinny had been the standard for a couple of decades, Keymod emerged on the market. Keymod rails quickly gained popularity due to their lightweight skeletonized design. They are also much thinner than Picatinny rails. People who already have Picatinny accessories can use Keymod adapters and Picatinny rail sections instead of purchasing new accessories. The Keymod design is considered open source to the public, so it can be used and standardized by the firearms industry. M-LOK, which stands for “Modular Lock,” is the newest mounting system, created by Magpul Industries. Although M-LOK is not open sourced like Keymod, any manufacturer can obtain free licensing with permission from Magpul. M-LOK currently seems to be the most popular, with Keymod trailing not far behind.

For a more in-depth analysis of handguards and rail systems, ARBuildJunkie has an excellent article on the topic.

Firefield M-LOK rail system increases space on your rifle for accessories.
Firefield Verge M-LOK Rail 7

Installation of Drop In Rails

The difficulty of installing a new rail depends on how it is mounted. Drop-ins are typically mounted very easily. Most times, drop-in rails can be installed with basic hand tools or none at all. The delta ring (or slip ring on “retro” rifles) needs be pulled back all the way to the rear, which will provide enough slack for the stock handguards to come loose. The new rail should be inserted in the reverse order that the old one was removed. The forward part of the rail should fit underneath the endcap located to the rear of the front sight/gas block. Pull the delta ring back and align the two halves of the rail.

Firefield Drop-in rail system comes in 2 separate pieces.
Firefield Edge Carbine Two-Piece M-LOK Rail (A ‘drop-in‘ rail)

Installation of Free Float Rails

Free float rails can be more difficult to install and may require the use of tools. This process typically requires the removal of the barrel nut and possibly the barrel, so supervision or installation by a certified gunsmith is recommended. First, the old furniture must be removed. Installation may also require the removal of the muzzle device, gas block/front sight base, and handguard endcap. Once the furniture and any necessary small parts are removed, the barrel nut needs to be removed using a barrel nut wrench or AR armorer’s wrench. Once the barrel nut is off, the delta ring assembly can be removed. If the barrel needs to be serviced or replaced, now would be the time to do so. The new barrel nut that came with the rail should now be installed and torqued down to proper specs outlined by the manufacturer. If the rail is not designed to work with an A2-style FSB, a low-profile gas block should be purchased and installed, along with all gas system parts. Longer handguards that extend over the gas block, like the Firefield Verge Slim rails, are becoming increasingly popular. The handguard end cap can now be discarded or set aside as it will not be needed. Once the gas system is reinstalled, the rail can be slipped over the barrel and attached to the barrel nut. Final attachment method varies between different rails as some are clamped down onto the barrel nut and some are attached via screws—refer to the manufacturer instructions for this process. Once the rail is attached to the barrel nut and properly torqued, the muzzle device can be reinstalled, completing the installation process. At this point, a certified gunsmith should check the rifle for proper installation.

If you wish to learn more, ShootingSportsRetailer has a great article on this topic.


Rails are a great option for those who want to “modernize” their rifles. They allow for easy mounting of essential accessories like lights, lasers and grips. Having extra real estate on a rail can also help with stability, depending on the shooter’s grip and shooting stance. Finally, it is important to remember that upgrades and modifications do not make a person a better shooter—training does. So once that rail is installed, hit the range and get training!

If you want to hone your shooting skills, OutdoorLife has an excellent piece on training and improving accuracy.