Custom AR-15 Components: Choosing Quality Parts

An AR-15 is an easily customizable weapon which can be built to meet your exact needs. There is an abundance of interchangeable parts and Custom AR-15 Components you can use to make this firearm fit your unique needs and wants, making it extremely versatile.

The AR-15 is an easily customizable weapon, which can be built to meet any shooter’s exact needs. There is an abundance of interchangeable parts and there are many configurations that can be implemented to build the perfect gun for the job. There are several common mistakes that people who are new to the AR platform make when customizing their AR-15. Some examples of these mistakes include ordering the wrong product, improper pistol grip installation, handguard interface and barrel nut incompatibility, incorrect hammer and trigger pin diameters, improper gas tube lengths, and an incompatible muzzle device thread pitch.

General Incompatibilities

An AR-15 upgrade may be purchased as a part, an assembly, or a complete kit containing multiple parts. To ensure compatibility, carefully review the product description before purchasing any upgrades. It is also a good idea to contact the manufacturer or consult an AR-15 expert if you have any questions.

Pistol Grip Installation

It is also very important when upgrading a pistol grip to properly install the pistol grip, safety selector, spring, and detent. If these AR 15 parts are missing or incorrectly installed, the safety selector will not operate smoothly, and the spring could even become permanently damaged and useless.


There is an overwhelming number of options for upgraded AR-15 handguards. Many handguards, especially free-floating ones, are not compatible with the original barrel nut, so it is crucial to ensure that the proprietary barrel nut (and installation tool if required) is included or purchased with the upgraded handguard. Attachment interfaces are also a consideration that must be made. There are three common handguard attachment interfaces and a large variety of accessory options for each one. The three common interfaces are Magpul’s MLOK, KeyMod, and the MIL-STD-1913 Picatinny rail.

Trigger and Hammer Pins

A less common but still possible issue is the purchase of incorrect trigger and hammer pins. From 1991 to mid-2009, Colt manufactured lower receivers that used .170” diameter trigger and hammer pins. If your AR-15 isn’t a Colt, don’t buy pins labeled as large or .170”. However, if your AR-15 is a Colt, simply verify the pin diameter with a digital or dial caliper before upgrading fire control group parts.

Gas Tubes

Gas tubes can occasionally become worn or damaged with heavy or long term use, and there are four different gas system lengths to choose from: pistol (6-3/4”), carbine (9-7/8”), mid (11-7/8”), and rifle (15-1/8”). Measure your gas tube before replacing it to guarantee a successful replacement. The lengths provided are approximate.

Muzzle Threads

AR-15 muzzle threads are typically determined by the caliber of the barrel. The most common AR-15 caliber is .223 or 5.56 NATO and will have 1/2″-28 threads while barrels chambered in larger calibers will usually have 5/8”-24 threads. There can be exceptions, so you should verify thread pitch before purchasing a new muzzle device. Threads are fairly easy to measure. Consult a local gunsmith, machinist, or your rifle or barrels manufacturer if you are unsure.

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