How to Replace an AR-15 Lower Receiver

Replacing the stock AR-15 lower receiver with a new unit, such as Brigade Manufacturing’s custom AR-15 lower receiver, is a simple process that most competent gun owners should be able to accomplish in a fairly short amount of time.

Some tools that will help are roll pin punches in sizes 3/32 inches, 1/8 inches and 5/32 inches to help drive out the pins. A small hammer used to gently tap out the roll pins also helps speed up the process. Roll pin holders also can be helpful as would a pair of needle-nose pliers. Also helpful is a No. 10 flat-blade screwdriver for removing the A2 stock screw if the rifle is so equipped and to remove the pistol grip if necessary. An Allen key also might be necessary for removing some stock grips with the size varying.

A very helpful tip is to systematically remove each part and immediately install it in the corresponding location on the new AR-15 lower receiver. Doing so will help even a novice owner of an AR-15 to properly install each part in its correct location without risking mixing up parts and putting them in the wrong location.

When disassembling an AR-15, removing a few pins generally is all that is needed to strip down the firearm so the lower receiver can be replaced. Removing the magazine is the first step and is no different than when changing magazines when reloading.

The next step is to separate the upper and lower receiver. The upper receiver contains the firearm’s bolt and barrel while the lower receiver contains the trigger and magazine well. For federal licensing purposes, the lower receiver itself is considered to be a firearm and will have its own unique serial number and must be transferred through licensed federal firearms dealers in accordance with federal firearms laws.

The upper and lower receivers are connected by a takedown pin and pivot pin connecting the lower receiver to the rest of the firearm. The takedown pin is located along the upper part of the lower receiver near where the butt stock is attached to the firearm. Pressing on the pin from behind or gently tapping it using a roll pin punch and hammer will back out the pin and its spring and allow the lower receiver to be swung down. Fully removing the takedown pin and spring can be done after removing a detent that prevents the pin from coming out fully. Once the detent is removed using a roll pin, the takedown pin can be removed as well.

The pivot pin is located along the upper front part of the lower receiver where the unit is pivoting and also can be removed along with the pivot pin spring by using a roll pin punch to allow the entire lower receiver to be separated from the rest of the firearm. The pivot pin also has a detent preventing full removal without removing the detent, first.

Once the lower receiver is removed, several items must be removed in no particular order so the new lower receiver can be installed. Immediately installing each part on the new lower receiver will be make the job much easier to accomplish. The rear stock and buffer tube must be removed as well as the buffer assembly, although complete disassembly is not necessary unless taking the time to clean and maintain the parts.

Removing the pistol grip also is necessary, and the hammer and its spring need to come out, which requires removal of the hammer pin. Also needing removal is the bolt catch along with its plunger, spring and roll pin and the magazine catch, and the safety selector lever.

The trigger is removed by taking out the trigger guard and its roll pin along with the trigger pin and trigger spring. When removing the trigger it will be necessary to also remove the disconnector and spring. The final item to come out is the magazine catch button and its spring.

Once all items have been removed and installed on the new lower receiver, it’s simply a matter of installing the pivot pin and spring, swinging the new lower receiver into position and installing the rear takedown pin as well as pistol grip and buttstock.