Welcome everyone to the TFB Armorer’s Bench! As mentioned in the little blurb, this series will focus on a lot of home armorer and gunsmith activities. In this article sponsored by Wheeler, Tipton, Caldwell, and Frankford Arsenal, we’ll show how to completely disassemble an AR15 lower receiver. I am well aware that most of the folks who pass through these parts are into the new, cool, and tacticool. I personally love older and obsolete stuff but I also like to take things apart and put them back together. That being said we here at TFB thought it would be nice to have a resource available for disassembling and assembling an AR15. Smith & Wesson was gracious and kind enough to help us out and sent us one of their Sport II models. I asked for a very simple and frequented offering to demonstrate common upgrades and general assembly when we get to that point but for now, let’s rundown a complete AR15 disassembly!
Disclaimer: It is stating the obvious when I say do not attempt this if you do not have confidence you can. There is no shame in not taking your gun apart. Consult a competent gunsmith/armorer for advice or if they would do the goal you wish to achieve. Refer to the first Armorer’s Bench article So, You Like Taking Guns Apart? where we talk about knowing your limitations.
TFB Armorer’s Bench: Complete AR15 Disassembly – Lower Receiver
Welcome to our recurring series of Armorer’s Bench which is made possible and brought to you by Wheeler, Tipton, Caldwell, and Frankford Arsenal who are our sponsors. Here, we at TFB hope to inform, entertain, and even inspire any would-be gunsmith or armorer out there. Ideally, with the information I provide and with the help of our sponsors, you can have some useful knowledge pertaining to the conservation and improvement of firearms technology while at the same time sharing experiences and teaching each other new tips and tricks along the way in the comments. Digging deep into what it is to be an armorer or gunsmith has significance but what is important is what those people do to show they’ve earned that title. I am happy to share my experiences and knowledge and hope it is informative!
Make your personal safety a priority:
- Practice proper gun safety. Always make sure before the firearm hits your bench that it is unloaded and safe to be handled.
- Wear the proper safety equipment. The main one would be safety glasses (decent ones) since parts are often under spring tension and you may work with high RPM tools. Other honorable mentions would be latex gloves or a respirator when working with potentially harmful solvents and oils. Also hearing protection when working with loud machinery or test-firing firearms.
- Modifications, alterations, and customizations will void your firearm’s warranty 9.5 times out of 10. Please take that into consideration before attempting any at-home gunsmithing.
- If you are unsure about proper safety practices, disassembly procedures, or warranty standards, stop, put down the tools, and consult a competent gunsmith.
Step One: Complete AR15 Disassembly – Lower Receiver
The first thing is first! Safety. Yes, I know safety is boring and sooo mainstream but bear with me. Make sure your firearm is unloaded. Check the chamber, magazine, and space between. Then check again. As far as PPE, I highly recommend wearing safety glasses at the very least. Multiple parts in an AR15 are under spring pressure and are commonly flung across a room and it would sure suck to take one to the face or eye.
Step Two: Complete AR15 Disassembly – Lower Receiver
Now that safety is out of the way, let’s separate the upper assembly from the lower. Take note of the two pins holding the two assemblies together. The pin at the rear is called a takedown pin and can be depressed left to right (it is captive so it cannot be driven fully out). When this is done be aware that the upper can pivot forward.
The front pin (called the pivot pin) can now be driven left to right (it is captive so it cannot be driven fully out). The upper can now be separated from the lower. I will set the upper aside and disassemble that in a future part of this string of articles.
Step Three: Complete AR15 Disassembly – Lower Receiver
I always try to work back to front on the receiver. If you have an adjustable buttstock they typically all come off the buffer tube the same way. A peg needs to fit into each individual adjustment hole and this is the only thing keeping the adjustable style stock on the tube. One way or another the peg needs to be pulled downward to clear the holes as well as the rear wall at the back of the tube.
With this stock, I pull firmly down on the adjustment lever at the bottom of the stock and slide it off the back.
Step Four: Complete AR15 Disassembly – Lower Receiver
Now that the stock is off, we can take the buffer and buffer spring out of the buffer tube. Take note of the buffer retainer in the picture below. The buffer retainer keeps the buffer and spring from shooting forward and out of the tube. This retainer needs to be carefully depressed to release the buffer and spring.
With a palm, finger, or thumb held over the buffer, depress the buffer retainer with a wide punch (I would recommend a nylon one to lessen the chance of slipping off). With the retainer depressed, let the buffer and spring out slowly.
Remove the buffer and spring from the buffer tube.
Step Five: Complete AR15 Disassembly – Lower Receiver
The stock lock ring or “Castle Nut” can now be loosened and backed off the receiver endplate. The best way to do this is to use an AR15 combination wrench with the castle nut end. Wheeler has a couple excellent options for wrenches. I would not recommend using anything other than a tool made specifically for the castle nut.
Most castle nuts are staked in place and can be pretty tight. Using a different tool risks your part’s well-being.
Besides using the right tool for the job, it would be best to have the lower in a vise or jig in order to hold it in place while loosening the nut. Tipton makes the Ultra Gun Vise with a build-in mag well vise. If you do not have a vise you can take a magazine that you are alright with potentially harming, inserting it into the mag well, laying the lower on its right-hand side, and then putting the wrench on the nut while pushing downward (the nut should be moving counter-clockwise).
With a good amount of pressure, the nut should loosen. Be careful and do not immediately start to unscrew the castle nut all the way back since its pressure is holding the backplate against the back of the receiver and a spring and plunger are hidden in-between.
Note: be aware that if you begin attempting to unscrew the buffer tube (and somehow succeed) you run the risk of losing the buffer retainer which is held captive by the lip of the buffer tube.
Step Six: Complete AR15 Disassembly – Lower Receiver
With that spring and plunger in mind, you can back the castle nut off toward the rear of the buffer tube. This will allow the backplate to slide rearward as well.
Take care not to scrunch, stretch, or crimp the spring. This spring provides pressure to a plunger that pushes against the takedown pin and keeps it captive in the lower receiver. The takedown pin spring can be pulled out of the back of the receiver and with a little persuasion (and tapping on the side of the receiver) the plunger should fall free as well.
Do not worry if you lose or harm these small parts. There are many companies that sell “oops kits” that include extra springs and plungers. Many replacement/upgrade parts will come with them as well.
Step Seven: Complete AR15 Disassembly – Lower Receiver
With the takedown pin, spring and plunger removed, the takedown pin itself can now be pulled out of the side of the receiver.
Step Eight: Complete AR15 Disassembly – Lower Receiver
From here the buffer tube can be unscrewed from the receiver. BUT! Make sure to capture the buffer retainer and retainer spring in some way.
This can be done by putting a large punch or flat of a screwdriver over the top and depressing the retainer while unscrewing the tube. If you are not comfortable with that method and would like the use of both your hands, an easier way would be to pack a rag over the top of the retainer in order for the spring pressure to be dissipated gradually as the buffer is unscrewed from the receiver.
Remove the buffer retainer and retainer ring.
Step Nine: Complete AR15 Disassembly – Lower Receiver
With the buffer retainer and spring out of the way, the buffer tube can be fully unscrewed and taken off of the receiver.
Step Ten: Complete AR15 Disassembly – Lower Receiver
Remove the endplate from the buffer tube by sliding it forward. The castle nut can stay put if you plan on putting this same tube back on a receiver.
Step Eleven: Complete AR15 Disassembly – Lower Receiver
Now we can move down the pistol grip. This part has two separate jobs just like that endplate on the back of the receiver did. The pistol grip is holding a hidden spring that provides pressure to a plunger that in turn gives the fire/safe selector switch both positive positions and also captive retention.
For this specific AR15, a 3/16 hex bit is needed for the hidden screw inside the pistol grip.
Be aware that while unscrewing the pistol grip screw that the spring that is hidden in between the grip and receiver will start to reveal itself. I recommend unscrewing the grip with the AR15 either on its side or upside down with the top of the receiver resting on the bench.
Typically the safety detent spring will tag along with the pistol grip upon removal.
Take note that once the spring is removed from its hole in the receiver, the detent plunger that the spring normally provides pressure to is capable of falling free if the receiver is bumped or placed in its normal orientation.
Remove the detent. If it is stuck, you can tap the receiver with a nylon or wooden handle of a screwdriver or hammer and the concussions should let the detent drop free.
Step Twelve: Complete AR15 Disassembly – Lower Receiver
From here there should no longer be anything preventing the safety/fire selector from being removed out the side beside its own orientation. The simplest way of removal is to spin the selector while pulling on it gently and it should pull free from the frame.
Step Thirteen: Complete AR15 Disassembly – Lower Receiver
With the safety selector out of the receiver, we can move onto the trigger and hammer assemblies.
First either put your palm over the hammer or shield the frame in front of the hammer with something to cushion it to prevent damage to the hammer or the frame.
Wheeler and Tipton both have magazine-style AR15 vises that have a rubber stopper that can be placed in the path of the hammer to release it and prevent it from causing any harm or damage.
With the hammer down and some spring tension (not all of it) released, we can begin its removal. With a 1/8 brass or nylon punch you may place it over the hammer pin and drive it out in either direction. I typically will do this left to right.
Note: the use of a bench block is highly recommended when punching out the hammer and trigger pins. Something as simple as a hockey puck can be used otherwise Wheeler has a really nice block specifically for AR15 receivers.
Once the hammer pin is punched out it is common for your punch to be held in its place by the remaining spring tension.
To prevent the hammer and its spring from being flung across the room when the punch is pulled out, I recommend draping a rag over the opening in the receiver in order to catch all that comes out.
Step Fourteen: Complete AR15 Disassembly – Lower Receiver
With the hammer and its spring out, we can take out the trigger, trigger spring, disconnector, and disconnector spring. These are all held in by the same pin but the last two are the parts to worry about. I always drape a rag across the top of the receiver in the event I slip or some freak thing happens that allows the disconnector and its spring to take flight.
With a bench block, light hammer, and nylon or brass punch, punch out the trigger pin left to right.
Once again the punch will most likely be held in place by spring tension and releasing the tension will launch the trigger assembly. Make sure you have something above the receiver opening to catch these parts.
Take note of the orientation and relationship of the parts in the trigger assembly.
Now note the relationship the trigger assembly has with the hammer assembly. Remember it is always good to take pictures while you do this just in case you need them for reference later.
Step Fifteen: Complete AR15 Disassembly – Lower Receiver
Onto taking out the bolt catch, its plunger, and spring. This part is the real pain for some folks and often the source of scratches and marring on the side of a receiver. Since it requires you to punch out the roll pin parallel to the receiver, it is best to have a roll pin punch and this roll pin I believe is a 3/32 pin.
Wheeler makes an awesome set of punches specifically for the bolt catch that have a flat rubber-coated side so you can avoid damaging your receiver. If you do not have these punches, you can simply wrap one in something like electrical tape and be very careful.
When punching out this pin, keep an eye on where it falls so you do not lose it.
With the punch still in the spot where the roll pin once was, it is still holding in the bolt catch and its spring and plunger. Once again I recommend placing a rag or cloth over the top of the parts and then pull out the punch and capture the parts.
Step Sixteen: Complete AR15 Disassembly – Lower Receiver
Now onto the magazine release button. This one is an easy one. Simply depress the magazine release button as deep as you can with a punch or eraser end of a pencil.
This will make the opposite end protrude proud of the left side of the receiver.
While the button is being pressed rotate the magazine catch lever counterclockwise until it is fully unscrewed and pulls free.
Let off of the magazine release button slowly and take out the button and spring.
Here is the relationship between those parts.
Step Seventeen: Complete AR15 Disassembly – Lower Receiver
The final piece of this lower is the front pivot pin which is being held captive by a hidden spring and plunger. The pivot pin has a built-in means of disassembly in the form of a hole in the pin itself.
Simply put a 1/16 punch in the hole at the front of the pin and use it to depress the pivot pin plunger.
When the plunger is depressed you can rotate the pivot pin upwards or downwards in order to bypass the plunger that was depressed.
Use a rag or your palm to cover the front of the receiver as you pull the pivot pin out of the receiver. The spring and plunger are under spring tension and are amongst the parts that get lost most often.
Honorable Mention – Complete AR15 Disassembly
This Smith & Wesson Sport II lower receiver has a fixed trigger guard. It is a part of the frame and cannot be changed. If you are dealing with another lower receiver that has a removable trigger guard, the disassembly is thankfully fairly easy as long as you practice patience. The rear pin is almost always a roll pin that should be punched out using a bench block or some other form of support under the guard so it does not bend. The front of the trigger guard however can be different. Some are in place by a simple screw to be unscrewed and others are similar to the pivot pin in which you depress a captive spring-loaded plunger.
End of The Lower – Complete AR15 Disassembly
I hate to leave anyone hanging with just the lower disassembled but the upper will have to wait for a separate week. If anyone has their own tips and trick or recommendations for anyone out there that needs a hand with lower disassembly feel free to talk amongst each other in the comments. Maybe at some point, we can do a separate tips and tricks article! Keep in mind that some folks may be new to this sort of thing and be considerate of any questions they may have. Thanks for tagging along so far and see you next time!
As always, thank you for reading TFB! Be safe out there, have fun while shooting, and we will see you next time for the TFB Armorer’s Bench brought to you by Wheeler, Tipton, Caldwell, and Frankford Arsenal! Also, let us know what you think in the comments below! We always appreciate your feedback.
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