Building Your AR Lower Receiver

By CTD Rob published on in Firearms, How To

So, you finally bought a stripped lower receiver and all the goodies that go along with it.

You excitedly tore open the box and checked to make sure we shipped you all the parts you needed to put together your first AR lower. You glare at the pile of parts and think to yourself, “Now what?”

Last year, we produced a series on how to put together the complete AR-15 lower receiver. As most of you know, the lower receiver houses the magazine catch, bolt catch, pivot pin, fire control group, trigger guard, selector, grips, pins and buffer tube. We still field a ton of questions about how to put these parts together, so we thought a rehash was in order. Installing these parts is fairly simple, and most people can do it without too many issues. However—when working on any firearm—if at anytime you feel you aren’t sure about what you are doing, take it to a qualified gunsmith.


Step 1: Installing the Magazine Catch


Step 2: Installing the Bolt Catch


Step 3: Installing the Pivot Pin


Step 4: Installing the Fire Control Group


Step 5: Installing the Trigger Guard


Step 6: Installing the Selector and Pistol Grip


Step 7: Installing the Takedown Pin and Buffer Tube


Stay Tuned!

Hopefully, this clears up some of the confusion. Once you do this a few times, most of the steps will become second nature. Stay tuned for more posts on AR builds. We’re going to pull some parts from the warehouse so we can throw together some uppers and barrels to see what we can come up with!

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Comments (38)

  • robert


    great detail


  • Kerry K


    Step 5, NEEDS to be changed.

    Never, NEVER, hit or try and drive in the trigger guard roll pin into a tab WITHOUT having something [such as the trigger guard itself] or a fitted block BETWEEN both tabs!!! They WILL BREAK OFF!!! If you can’t put the roll pin in place and drive it in by holding EVERYTHING IN PLACE, then place the lower receiver on a hard flat surface, such as a work bench, and put a small hard piece of wood UNDER the lower tab and the adjacent part of the rear lower receiver. NOTE – the lower tab, as the receiver sits on the work bench, should be flat on the piece of wood. If there is space on one side, find a different piece of wood or cut a piece to match the height of space between he work bench and the tab. DO NOT put the wood just under the tab itself. With the lower receiver sitting on the bench with the small block of HARDWOOD in place, AND the trigger guard in place, then, and only then, drive in the trigger guard roll pin.

    Again, NEVER, NEVER, drive in the roll pin without supporting the lower receiver [such as shown in the this video] AND having the trigger guard itself in place. You WILL break off a tab. I’ve seen it done!!!


    • Marine Gunner


      Excellent advice! That tiny discrepancy aside, this is an outstanding tutorial. After having been trained on the M-14, the first time I was issued an M-16 (AR-15) it seemed very complicated and I was a little intimidated. Wish I had this tutorial back in the day. Very well done.


    • Kerry K


      Very true Marine Gunner, these videos are SUPERB!! I shot an AR15 about 25 yrs ago and then never had the money to go out and just buy one till they came out with receivers and kits. Bought a receiver and a full kit a few years ago [upper was already complete and assembled] and then carefully laid everything else out on the work bench. WHERE to start, I thought!!! LOL!! With no instructions what-so-ever, just started visualizing where everything should go and how it should go together, then dove in!! Rather than driving in the roll pin for the trigger guard, I used a set of channel locks, and with the trigger guard in place, I squeezed the pin in place, AFTER oiling the heck out of it. It went in slicker than sh*t, or maybe I should say “snot on glass”, either way, it was a snap. :-) If any of you can get to a gun show, lower receivers are down to about $60 now and full complete kits can be picked up for less than $600, so there isn’t any excuses in not having an AR!! Happy Building!!!


    • James R


      I just bought a Bushmaster AR-15 at the local Dunhams Sporting Goods store for $499. So for the best price I have ever seen on them I am now a member of the club. I put a 3×9 scope on it and laser bore sighted it. I love this gun.


  • Gary


    Really nice job on breaking down the assembly process into sections will have to check and make sure my MOE trigger guard came with that screw. Will be assembling my Lower tonight if my LPK arrives.


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