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 (45)

  • SgtRed


    Nice hands! Is that fellow a hand model?


  • Russ


    Very well done, I will recomend it to my customers. Awaiting the video on the uppers as well. Thanks


  • james


    very informative thanks james


  • Bill


    Great basic information! Very helpful and appreciated. Many that own ARs are honestly too scared to do anything past a cleaning breakdown – this gives a chance to become much more comfortable with your firearm. Thanks!


  • Gungearman


    Castle nuts vary from manufacturer to manufacturer. I’ve read the reviews on all of the different wrenches that CTD sells, and all seem to fit different nuts on different brands. Are the teeth too thick or tall? Some other customers filed the teeth to fit their gun.

    It’s very common for this to happen. I use something very similar to this wrench on many builds, using the single ‘tooth’ part:


  • Don


    Appropriate wrench for castle nut? I bought a Tapco wrench for my S&W AR15 Sport (mil-spec) and the wrench does not seem to fit castle nut. It seems that I will damage the nut and possibly the threads if I attempt to engage the wrench. What is wrong?


  • James Madsen


    Very good info . To a newcomer this is what is needed. Thanks a lot.


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