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How to Build an AR-15 Lower Receiver [Ultimate Visual Guide]

Don't want to mess up? Learn how to build an AR-15 lower receiver with 80+ pictures, tricks I learned the hard way, and recommendations of the best parts.
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    There’s nothing like assembling your own AR-15 lower receiver for personal satisfaction and customization.

    I’ll guide you through everything with minimal tools and tons of tips I’ve learned the hard way!

    Complete AR-15 Lowers
    Complete AR-15 Lowers

    So get ready for A LOT of pictures that will make building your lower a breeze. Plus a bonus of the upgrades I immediately did to my lower to make it perfect for 3-Gun competitions.

    But first…a disclaimer that this is for educational use only. If you don’t have the right tools or experience, please have this done by a professional or buy a completed rifle (Best AR-15 Buyer’s Guide).

    Table of Contents

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    Parts and Tools

    Parts

    All AR-15 Lower Receiver Parts
    All AR-15 Lower Receiver Parts

    I went with a California featureless build so there’s the funky looking grip.  But otherwise, everything is pretty standard.

    I haven’t found much difference between lower parts kits and buffer tube assembly’s as long as there are decent reviews and not a no-name company:

    Most Affordable
    35
    at Kygunco

    Prices accurate at time of writing

    Prices accurate at time of writing

    Available Coupons
    Lower Kit, ar15.com
    Lower Kit, ar15.com

    Tools

    • Punch Set ($15): I prefer brass so you don’t mar up your lower receiver and it’s good for lots of other gun stuff too
    • Long Arm Hex Key Set ($12): You’ll be using hex keys or Allen wrenches in a lot of installations.  Go with the long arm versions for extra reach.
    • Hammer ($10): I like the rubber/plastic ends instead of standard steel since there are very few times when you actually need that much force…also if you use it directly on gun parts, you will not mar the finish
    • C-Clamp ($10): Not super necessary but useful to install the trigger guard, 4-inch should be good
    • AR-15 Combo Tool ($20): Good for installation of the castle nut, but more useful for upper receiver builds
    • Utility Knife ($7): Needed for the pivot pin installation
    Magpul Armorer's Wrench
    Magpul Armorer’s Wrench

    Alright, let’s get onto the actual build!

    Magazine Catch Assembly

    Magazine Catch Assembly Parts
    Magazine Catch Assembly Parts

    You can start your AR-15 lower receiver build many different ways but I like knocking out some of the easier ones first for quick wins.

    Find these three parts along with your lower receiver. The magazine spring is the largest width spring in your kit.

    Magazine Release Spring
    Magazine Release Spring

    Place the magazine release spring into the hole shown above.

    Magazine Release Button
    Magazine Release Button

    Place the magazine release button on top of it with the serrated side up.

    Magazine Catch
    Magazine Catch

    Press in the magazine release button and flip the receiver over to start threading in the magazine catch.  

    It might be a little tricky the first time you do it since you have to maintain decent pressure on the button to make it flush against the receiver while matching up the threads. Righty-tighty!

    Make sure the catch doesn’t scrape against the raised portions of the receiver.

    Screwed in Magazine Release
    Screwed in Magazine Release

    Once you have it threaded slightly you can release the pressure and rest your fingers for a little.  

    Then get ready to do it again!  

    Press down the magazine release even further into the receiver past the flush line and tighten the magazine catch a couple more times.

    Gap Between Magazine Catch and Receiver
    Gap Between Magazine Catch and Receiver

    Check once in a while.  

    Here you can see that there’s a gap between the mag catch and the receiver when you’re pressing the mag release button flush.  

    You’ll need to tighten more or else the mag catch could fail to go back into the receiver during a reload.

    Correct Distance for Magazine Catch
    Correct Distance for Magazine Catch

    This is a good distance where the magazine catch will not leave the receiver unless somehow you manage to really smash in the magazine release button.  

    You can test with some of your mags to make sure it catches and releases.

    Congrats! You’ve installed the first section of your AR-15 lower receiver.

    Trigger Guard Assembly

    Some lowers have this part as part of the stripped lower…but most likely you’ll have to do it yourself.

    Trigger Guard Assembly Parts
    Trigger Guard Assembly Parts

    Find the trigger guard and the longer roll pin.

    Depress Pin of Trigger Guard
    Depress Pin of Trigger Guard

    Depress the pin of the trigger guard which will be closer to the magazine well.  

    Don’t worry, the two sides are differently sized so you can’t mess it up. Then just slip it in.

    One Side of Trigger Guard In
    One Side of Trigger Guard In

    Sometimes I find that the other side has a hard time dropping in so I lightly press down or even use the plastic hammer (lightly) if it’s slightly more stuck.

    Roll Pin for Trigger Guard
    Roll Pin for Trigger Guard

    Make sure everything is lined up for the roll pin.

    Start Roll Pin with Hammer
    Start Roll Pin with Hammer

    You can either start it with the hammer, with a punch, or just with your fingers. I like using the hammer to get started then using the C-Clamp below.  

    It’s much easier than trying to hold down the receiver while hammering.

    Note: If you decide to go with just hammering…make sure you are supporting the dog ears or else they can pop off pretty easily even on a good quality lower.

    Finish with C Clamp
    Finish with C Clamp

    I did end up marring my finish a little so I would heavily suggest using some plastic. (I’ve heard a little piece of milk carton plastic between both sides of the clamp will do wonders.)

    Installed Trigger Guard
    Installed Trigger Guard

    On my installed trigger guard, you can see a little damage to the finish. But I know I’ll be dealing a whole lot more damage to the receiver at the range and during competitions.

    Bolt Catch Assembly

    Bolt Catch Assembly Parts
    Bolt Catch Assembly Parts

    Find these parts! 

    The bolt catch spring is even throughout while the other remaining smaller spring is fat on one end for the disconnector.

    Bolt Catch Spring and Plunger
    Bolt Catch Spring and Plunger

    Place the spring on the plunger and drop it into the hole above the magazine latch.

    Bolt Catch
    Bolt Catch

    Orient the bolt catch like above and drop it down.

    Bolt Catch Roll Pin
    Bolt Catch Roll Pin

    You will need to depress the bolt catch for everything to line up. I like using a hammer and punch to get it started.

    Squeezing the Bolt Catch Pin
    Squeezing the Bolt Catch Pin

    Apparently, there’s a special tool to clamp the roll pin but I decided to make my own.  

    However, it wasn’t protective enough so I would suggest wrapping your pliers with tape first then some cloth. Or you can just continue using the punch all the way through.

    Installed Bolt Catch Pin
    Installed Bolt Catch Pin

    The finished bolt catch with just a little bit of marring.

    That wasn’t so bad, right? The trigger coming up is a little tricky but don’t worry, I got you!

    Trigger Assembly

    AR-15 Trigger Assembly Parts
    AR-15 Trigger Assembly Parts

    Pick out these parts from what’s left.

    Correct Trigger Spring Orientation
    Correct Trigger Spring Orientation

    Attach the springs according to what you see above.

    Disconnector Spring In Fat Side Down
    Disconnector Spring In Fat Side Down

    Place the fat side down into the trigger so that the spring stays put.

    Disconnector Placement
    Disconnector Placement

    Place the disconnector onto the spring.

    Trigger Hole
    Trigger Hole

    Press down on the disconnector to see the trigger hole.  You’ll be placing this assembly into the receiver and then putting a pin through it.

    Placement of Trigger
    Placement of Trigger

    Place the assembly so that the trigger goes through the oval bottom of the receiver.

    Trigger Hole Through Receiver
    Trigger Hole Through Receiver

    Match up everything so that you can see the clear hole for the pin.

    Trigger Pin Almost Through Receiver
    Trigger Pin Almost Through Receiver

    I sometimes find the trigger pin has some trouble once it’s almost through. So, I resort to using a brass punch after matching it up.

    Installed First Trigger Pin
    Installed First Trigger Pin

    Here you see the fully installed first trigger pin.

    Double-check the placement of the hammer and spring. Make sure the springs lay on top of the first trigger pin.

    They’ll be decent pressure to align the second trigger pin hole.

    Trigger Hammer Pin Halfway
    Trigger Hammer Pin Halfway

    Once you get the trigger pin halfway through, I like cocking the hammer down so that it eases the pressure a little bit.

    Trigger Hammer Pin with Punch
    Trigger Hammer Pin with Punch

    It turned out extra stiff so I used the brass punch.

    Installed Trigger Hammer Cocked
    Installed Trigger Hammer Cocked

    Here’s the installed trigger assembly.

    Release Trigger with Finger
    Release Trigger with Finger

    Resist the urge to dry fire!

    Doing this will release the hammer which has nothing to hit except the lower receiver.  And enough of that will start to damage it.  

    I hold the hammer down with my other hand so that it slowly releases instead of slamming into the receiver wall.

    And there you have it…the trigger assembly!

    Safety, Takedown Pin, Grip, & Receiver Extension

    Still with me? We’re in the home stretch now.

    Safety, Takedown Pins, Grip, Receiver Extension
    Safety, Takedown Pins, Grip, Receiver Extension

    These should be the remaining parts in your kit. Note the different sizes of springs relative to each other. The two skinnier longer ones are identical for the takedown and pivot pins.

    Grip Holes
    Grip Holes

    Let’s start with the grip.

    The top one is a normal pistol grip while the bottom is the CA legal Hammerhead grip.  

    Both have holes for a screw and washer. You might just need a longer hex key for the pistol grip to reach all the way in.

    Cock Hammer Back
    Cock Hammer Back

    But first, let’s cock the hammer back so it opens up the safety selector hole.

    Insert Safety Selector
    Insert Safety Selector

    Insert the safety selector.

    Set Safety to Fire
    Set Safety to Fire

    Set the position to “Fire.”

    Safety Detent
    Safety Detent

    Find the safety detent (pointed side into the receiver) and put it in the hole on the opposite side of the safety indicator.

    Safety Detent Inserted
    Safety Detent Inserted

    A much better view of the silver safety detent installed.

    Spring for Safety Detent
    Spring for Safety Detent

    Find the safety detent spring. It’s the thinner one that is slightly shorter than the other identical thin springs.

    Insert Spring into Grip
    Insert Spring into Grip

    Insert it into the hole at the top of whatever grip you’re going to use.

    Spreading Apart Hammerhead Grip
    Spreading Apart Hammerhead Grip

    Sometimes the grip doesn’t fit on easily (nor do you want it to be loose). I find that using a big flathead makes it easier to slide onto the lower receiver.

    Matching Up Spring with Safety Selector Hole
    Matching Up Spring with Safety Selector Hole

    Match up the spring with the safety selector hole and double-check that the safety selector is still in the “Fire” position on the opposite side.

    Screwing in Grip
    Screwing in Grip

    Screw in the grip with the enclosed hex nut and washer.

    Shorter Rear Takedown Pin
    Shorter Rear Takedown Pin

    Look for the shorter pin (rear takedown pin) which will have an identical spring and detent to the longer pin (pivot pin).

    Install Rear Takedown Pin and Detent
    Install Rear Takedown Pin and Detent

    Install the rear takedown pin from the left to right (shown fuzzily, sorry!) and also place the detent in the back of the receiver.  

    It helps to orient the takedown pin so its “channel” will accept the detent.

    Insert Detent Spring
    Insert Detent Spring

    Insert the detent spring.

    Buffer Retainer and Spring
    Buffer Retainer and Spring

    Now find the buffer retainer and spring (thickest one left) and place them in the hole above.

    Placement of End Plate
    Placement of End Plate

    Also, take a look at your end place where one side has protrusions that will fit nicely with the back of the receiver.

    Castle Nut First
    Castle Nut First

    But first, screw on the castle nut in the position above. With the bigger square cuts toward the back of the lower receiver.

    End Plate on Buffer Tube
    End Plate on Buffer Tube

    Then put on the end plate in the correct orientation. I’ve definitely done this in the wrong order, so please learn from my fails!

    Screwing in Buffer Tube
    Screwing in Buffer Tube

    Start screwing in the buffer tube. The end plate will move with each turn and start messing with the spring.  

    Try your best to not let it come out.

    Almost Done Screwing in Buffer Tube
    Almost Done Screwing in Buffer Tube

    When you’re almost done screwing in the buffer tube, take a break to look at the other side.

    Buffer Tube Almost to Buffer Retainer
    Buffer Tube Almost to Buffer Retainer

    You want to stop right before the buffer tube reaches the buffer retainer.

    Buffer Retainer Active
    Buffer Retainer Active

    Perfect fit with just a little bit more of a turn.

    Match Up End Place
    Match Up End Place

    Now you need to match up the end plate with the receiver and also make sure that when the plate is tightened that it will hold the spring.

    Screw in Castle Nut
    Screw in Castle Nut

    Start screwing in the castle nut with your hands first.

    Tightening Castle Nut
    Tightening Castle Nut

    If you have an AR-15 armorer’s tool, it will have a section to tighten the square cuts. I’d heavily recommend that since it’s only a few bucks.  

    But otherwise, you can also just lightly punch it tight.

    Staked End Plate, ar15.com
    Staked End Plate, ar15.com

    You can also “stake” your castle nut where you use a center punch to smash in the end plate into the smaller cuts of the castle nut.  

    I would recommend testing out your lower a lot beforehand since it’s annoying to undo but really keeps it together. Also, make sure your end plate allows staking.

    Front Pivot Pin
    Front Pivot Pin

    Now find the last pin, screw, and detent that will be for the front pivot pin.

    Detent Spring In
    Detent Spring In

    Place the detent spring in first.

    Detent In
    Detent In

    Followed by the detent.

    Pliers and Razor to Hold Detent
    Pliers and Razor to Hold Detent

    Time to whip out the pliers and utility knife to hold the pin down flush against the receiver since you’ll be sliding the pivot pin over.  

    I’d recommend doing this in a sideways cardboard box or something above you to catch the potential flying detent and spring if you mess up. Also, you might want some eye protection.

    Insert Front Pivot Pin
    Insert Front Pivot Pin

    Insert the front pivot pin over the knife blade with the channel facing where the detent will spring out. This will install the pivot pin.

    Completed Front Pivot Pin
    Completed Front Pivot Pin

    Ta-dah!

    Stock, Buffer Spring, and Buffer
    Stock, Buffer Spring, and Buffer

    Now find your stock and buffer and buffer spring. Yes, it’s super ugly but I got it since it was the cheapest “color.”

    Buffer Spring In
    Buffer Spring In

    Insert the buffer spring in.

    Buffer End Out
    Buffer End Out

    The buffer end will orient like the above.

    Slide on Stock
    Slide on Stock

    Slide on the stock until it doesn’t move easily.

    Pull Tab to Engage
    Pull Tab to Engage

    Pull the adjustment tab out and continue moving the stock inwards. You can now use the adjustment tab to select your preferred distance.

    And YOU’RE DONE!

    Unless you’re in CA and want to pin your stock, then check out my How to Pin a Collapsible Stock Guide.

    But if you’re like me…you want to make your AR-15 lower receiver the best it can be. Here are the upgrades I added immediately.

    Ultimate 3 Gun Rifle Build
    Ultimate 3 Gun Rifle Build

    AR-15 Lower Receiver Upgrades

    AR-15 Lower Upgrades
    AR-15 Lower Upgrades

    JP Silent Captured Spring

    The JP Silent Captured Spring is one of the best upgrades to make your AR-15 feel like a pellet gun! It takes away the *sproing* of the traditional buffer tube and drastically reduces recoil.  

    If you’re going with a lighter BCG, I’d recommend getting it with the additional springs so you can truly tune your gun. Otherwise, the stock spring works great.  

    Check out how to Install & Tune the JP Silent Captured Spring in our article.

    Slide in JP Silent Captured Spring
    JP Silent Captured Spring

    Ambidextrous Safety

    An Ambidextrous Safety is useful especially when you’re running a CA featureless rifle, but if you’re a lefty it’s critical.  

    For tips, see How to Install Your Ambi Safety.

    Screw in Ambi Safety
    Screw in Ambi Safety

    Magpul BAD Lever

    The Magpul BAD Lever is on every single one of my lower receivers. It makes manipulating the bolt super easy from your right hand.  

    Install it in less than 5 minutes.

    Assembled BAD Lever
    Assembled BAD Lever

    Hiperfire Trigger

    Swapping out the trigger is probably the best upgrade you can do to your AR-15.  

    Hiperfire Eclipse Trigger
    Hiperfire Eclipse Trigger

    The Hiperfire Trigger is a new single-stage trigger that has no perceptible creep, little reset, adjustable weights (I run mine at the lightest 2.5-pounds), and actually increases the hammer strike power.  

    Hiperfire Eclipse 2.5 lb Trigger Pull
    Hiperfire Eclipse 2.5 lb Trigger Pull

    One of the weaknesses of other triggers is that while you can get light pulls, those sometimes can lead to light primer strikes too.  

    See my in-depth review. The installation was also much easier than I expected given the number of parts.

    Hipershoe Installed
    Hiperfire Installed

    Conclusion

    I know it seems intimidating but building your own AR-15 lower receiver doesn’t have to be scary. With this guide and the right tools, you’ll be ready to rock your AR-15.

    Lots of AR-15 Uppers
    Lots of AR-15 Uppers

    If you need more help in building your lower or your full AR-15 for that matter, check out Brownells’ series How to Build an AR-15 Tutorial.

    How did your first AR-15 lower build go? Let us know in the comments below. And pair this guide with our How to Build an AR-15 Upper Receiver and also check out the Definitive AR-15 Resource for even more upgrades, optics, etc.

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    159 Leave a Reply

    • Commenter Avatar
      Bill

      Here's another THANK YOU for this guide. I purchased 2 kits for myself and my Daughter. We followed this guide with the only real hassle we had was the trigger pin installation. I resolved this by cutting a 16D nail then using the point to pull the pieces into alignment. I installed the pin by using it to chase the nail through and out of the receiver. The balance of assembly went without issue except for a couple of flying detent pins and springs.

      September 16, 2023 4:48 pm
    • Commenter Avatar
      George

      Thank you very much for this guide. I referred to it constantly in building out my stripped lower. (Then later when I replaced the trigger/hammer group.)

      Excellent guide. I'd add that a set of vise-pliers is insanely useful, and that a buffer pin isn't absolutely necessary. (Complete coincidence that I came to that opinion after I launched the pin into orbit...)

      September 10, 2023 7:30 pm
    • Commenter Avatar
      Michael H

      I don’t know where I got the instructions to build my first lower, but these were a good reminder for the second. I can do it in about 40 minutes now.

      Alternate tips/thoughts:
      A spring grip clamp can hold the bolt catch down when installing the roll pin if necessary.

      Punches about the same diameter of any pin hole are your friend. A small punch can be used to seat and align the pinned trigger parts and bolt catch when installing pins.

      No brass? Wrap your punches in electrical tape. For starting the bolt catch roll pin I take a punch about three times larger than the pin and wrap it in electrical tape (the business end) with a little lip of tape hanging off the end and it can be used to protect your lower while driving the roll pin in, and the lip stops the punch from slipping off the pin.

      I have a Wheeler piviot pin installation tool that works great, but your method seems pretty fool proof too.

      My parts were coated in some sticky protective coating. I acetoned all of them before installing.

      Grease in the pivot and takedown pins helps them function.

      If you have a buffer tube with a cut-out for the buffer retainer pin, if you tighten the tube on too far—where the pin still engages, your upper might not seat, so check before cinching down the castle nut.

      May 9, 2023 11:06 am
    • Commenter Avatar
      Burns Sporting

      Thanks for the tutorial, I was able to build my 1st lower and subsequently built my 2nd one an hr later. Your step-by-step method is great, and I didn't have to spend any additional dollars on tools. I had everything laying around the house. Thanks again!

      April 1, 2023 3:22 pm
    • Commenter Avatar
      Kevin M

      Great write up!

      March 31, 2023 6:51 pm
    • Commenter Avatar
      miller machine shop

      Your article is quite helpful! I have so many questions, and you have answered many. Thank you! Such nice and superb article, we have been looking for this information about How to Build an AR-15 Lower Receiver. Indeed a great post about it!!

      March 3, 2023 7:26 am
    • Commenter Avatar
      Dominick

      Thanks a lot! This was awesome. Only thing that was a little unclear was how the hammer installed above the trigger. No picture showing that. Took a little trial and error, but finally got it.

      February 18, 2023 1:53 am
      • Commenter Avatar
        Rex B

        Installation of the hammer was omitted.

        September 4, 2023 2:21 pm
    • Commenter Avatar
      Peyton

      Great instructions! Put together my first build with only minimal tools. Very detailed instructions that help out a lot. Only thing I wanted more coverage on is the trigger assembly as I had to go to another video to see which way the hammer spring had to sit on top of the trigger pins. But other than that awesome!!!!

      January 19, 2023 8:47 am
    • Commenter Avatar
      Brandon Kollar

      Hello! I would like to share my instructional video I know images can be difficult but if anyone is struggling with their lowers or would like an in-depth guide and tutorial with a matching template Here it is! We sell two models a holding template instructional video with or without the parts kit! Over 1000 Units Sold today. Google Us! Bkollar Templates and use code: freeship2023 at checkout

      January 5, 2023 10:12 pm
    • Commenter Avatar
      dude

      The wording for installing the takedown pin is wrong. It installs right to left. Even though I know better, I was just following along without thinking as much as I should. Having to redo that detent and spring madness after you figure out you did it wrong is pretty frustrating. Otherwise, this was a great build guide. Just did my second lower build and other than the aforementioned mix up, this was helpful to have while I did it.

      December 11, 2022 12:40 pm
    • Commenter Avatar
      Robert

      I'm currently in the middle of my first AR pistol build and this guide is amazing. I build my lower from YT videos, but most do not go into detail on which spring and facing of components. I was able to verify I assembled my lower correctly.
      I went with Aero enhanced receiver and parts kit. This has a lot of set screws vs roll pins, which I found very handy and much simpler than I anticipated to assemble. Now the lower is assembled (although I will be removing some set screws to locktite them), I have an Aero buffer tube coming with Geissele Super 42 combo with H1 buffer, braided spring, and two tungsten weights to go H1-H3. I'll be purchasing the SBA4 brace to complete the lower.

      I'm still researching which upper caliber I'll build for my home defense. I'm considering 300 Blackout, 223 w/ 110 grain cartridges, 22LR or 22WMR, and 5.7 home defense (if the AR Five7 company ever begins manufacturing the 10" again). Speer has some interesting options for the 223 and 5.7 specific for home defense. Any suggestions are appreciated.

      December 6, 2022 8:11 am
    • Commenter Avatar
      John

      Thank you, your instructions are great. Put together my 1st AR all black and I'm super happy to say with zero Mark's, scuffs or scrapes. Thanks again for your expertise.

      October 25, 2022 5:45 pm
    • Commenter Avatar
      E

      So, I've built several lowers....and I always have this page open because it's awesome AF. Thanks, y'all!

      October 24, 2022 8:56 pm
    • Commenter Avatar
      Robert Kennedy

      This was helpfull for my first build. Only thing is i kinda had to back track a bit to get the upper on but after messing around with it i figure out how it goes. Over all i did get my ar15 built! Thanks

      October 4, 2022 4:43 pm
    • Commenter Avatar
      Scott Bancroft

      Eric, many thanks for this indepth walk-through! I only lost one detent pin, follow your advice as much as I could. A painless (relatively) effort!

      August 25, 2022 6:16 pm
    • Commenter Avatar
      John Parker

      Ordered a single point sling with the piece that goes behind the end plate ...don't know the name...so I thought I would take the buffet tube off....lol..not knowing bout the springs and parts that would fall off. So thank you Eric for the tutorial.

      August 5, 2022 9:52 am
    • Commenter Avatar
      SP

      Great article! Just finished my first lower build… aside from mixing up a takedown spring for my safety spring, it went without a hitch. Fixed my mistake, threw my existing upper on to check function, it’s rock solid. And was a lot of fun, too. Thanks!

      June 30, 2022 9:22 pm
    • Commenter Avatar
      ts

      I almost always replace the pivot and take-down pins with extended pins. That leaves me with the stock pins contained in most LPK's. I use the stock pivot pin inserted from the left side, and rotated groove forward, to hold the retainer and spring in place. Then just butt the extended pin's end against the 'helper' pin's end and push it into place.
      I've also found when doing this that it helps to have the extended pin started with the groove facing forward and once it is through the near-side lug I then rotate it until the retainer pin drops into the groove.
      HTH

      May 27, 2022 9:01 am
    • Commenter Avatar
      John Bonham

      Hello i found that using a small zip strip arond the trigger assembly to get it alined drop it in line it up put the pin in no messing with the 2 parts cut the zip strip and take it out

      April 9, 2022 5:26 pm
    • Commenter Avatar
      Barry

      first time build.....very helpful....great detail.....could use more close-ups.

      March 10, 2022 6:55 am
    • Commenter Avatar
      Randie Coulter

      Thank you very much for the great, and easy to understand, tutorial.
      I just finished assembling my first lower and it was really a breeze! I will be going back and making mods per some of the other replies.

      Again, thank you for this,
      Randie

      March 8, 2022 8:57 am
    • Commenter Avatar
      Texas_Suspect

      Thank you the the detailed pictures and instructions, youtube videos don't have the close ups that needed for this.

      February 19, 2022 10:08 am
    • Commenter Avatar
      sound awake

      1 get a cnc billet lower from primary arms or joe bob outfitters - they just look cooler and the bolt catch pin is a threaded allen screw - super easy to install
      2 get a razor blade and dull it down on the sidewalk and use in combination with an allen wrench the same size as the front takedown pin for installation of it - the razor blade holds the detent pin and spring down while you slide the allen wrench in from the opposite side and then just push it back with the takedown pin and it snaps right into place
      3 get a starrett center punch for staking the castle nut theyre 9 bucks on amazon and super easy to use

      November 15, 2021 4:20 pm
    • Commenter Avatar
      Keith P.

      There's a lot of super useful info here, well organized. A couple of suggestions for updating the pivot and takedown pin installation process:

      1. Just use a specialized pivot pin installation tool, especially for the front pin. It only costs about $11 at Walmart online and it will make the job a snap (and save you the cost of at least one emergency replacement parts kit). Every time you build an AR (or help a friend build one) you will be glad you did. Best $11.00 I have ever spent on gun tools, hands down.

      2. Cut about 1/4 to 1/2 inch off the takedown pin spring, especially for the rear one. This is doubly important if you use an Aero lower (or any brand that uses a set screw to secure the takedown pin spring, which adds even more compression). The standard length spring just pushes too hard on the detent into the takedown spring groove, and makes it really hard (damn near impossible, actually) to push out the pin with just your fingers.

      3. Use a little 1000 grit sandpaper on the head of the takedown pin detent, and in the takedown pin groove. And some grease in the groove of the takedown pin. Again, this makes the takedown pins work a whole lot better.

      October 26, 2021 9:54 pm
      • Commenter Avatar
        Keith P.

        Or even cheaper, use a 1/4 inch clevis pin and a 1/16 inch pin punch instead of special tools

        October 29, 2021 3:15 pm
      • Commenter Avatar
        John Martin

        I was looking for this because that was exactly my experience with 3 aero lowers. That rear takedown pin detent spring was just too long and I needed to trim it down. I'm using the Juggernaut Tactical Hellfighter mod kits and you need to turn that rear takedown pin. The new takedown pin also has a section cut out and too much pressure makes the detent skew the pin if you aren't super careful.

        March 15, 2022 7:41 pm
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      Richard Masyga

      I believe the description for installing the rear take down pin is incorrect. It says to install the pin “from the left to the right.” It should be installed from the right to the left - assuming left/right are looking at it as you would shoulder the weapon. The photo shows it correctly with the head of the pin on the right side of the receiver.

      August 24, 2021 5:15 pm
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      Big Nick

      Thanks for your excellent tutorial! I'm doing my first AR build and actually I'm finding it pretty simple. I build hot rod big Harley motors and scratch build custom bikes to put food on the table. A tip that may help others from losing small parts is to work on a piece of short knap carpeting or even a sheet. Also pre fit trigger and hammer pins in your lower, then for the final install, wiggle the hammer and trigger into full alignment and the pins will easily push in position with your fingers. As far as other roll pins, sometimes a number drill bit the same size as the pin OD can be used to enlarge the hole the first 1/4 into the ear. This will let the pin locate perfectly and prevent slips, gouges and damage to the lower. Also start pins in the first ear before installing the part to be pinned, it's much easier.

      August 21, 2021 8:10 pm
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      Big Tee

      I got an Aero LPK for 50 a couple months ago. Shop around!

      August 16, 2021 2:21 pm
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      Rp

      Just used this on my first lower. Thanks for the guide. The hardest part overall was the trigger guard pin, followed by the upper takedown pin spring. I didn’t listen to your advice and ended up losing one but thankfully my parts kit had a spare. As a total noob the hammer orientation wasn’t clear to me so I had to fall back to a video to get that part working.

      May 14, 2021 9:11 pm
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      JK

      Awesome experience for me to have this kind of guide for a noob like me. Thank you very much.

      May 4, 2021 7:56 pm
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      george

      Does the trigger disconnector ever need to be filed down at the bottom to get the pin to go through if it does not line up with different receivers and different disconnectors?

      May 3, 2021 5:14 pm
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        Tim W

        No, it just needs to be lined up correctly which can be a pain.

        May 22, 2021 1:24 pm
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      Meph

      You just helped me put together my 1st ever lower receiver in 2 hours or less. This was absolutely great, thank you.

      April 26, 2021 5:48 pm
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      Nu

      great details on assembly the AR-15. I like the detail that you've provided step by step. Awesome work.

      April 24, 2021 11:53 am
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      Dan Koehler

      Thank you for giving complete instructions, that are understandable

      April 23, 2021 6:11 am
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      JM

      thaanks for the help.
      im a techy guy, but this was beyond my scope when it come to assembling a rifle.
      now i know how.

      April 13, 2021 12:56 pm
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      Frank

      the beat tutorial video

      March 31, 2021 1:18 pm
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      Martin

      Thanks, just completed my first lower. Not having the exact tools, I found a few things that helped. Built on an Anderson lower using an LBE lower kit. The biggest issue (probably for all) was the roll pins. I used a Vise Grip 5WR (5 inch) which is one of the smallest to hold the pins. I lined up the pins right on the edge and used my hammer to strike the Vise Grips to start the pins. Once everything was lined up, I used an Irwin 7 inch clamp. Great tool, Rubber coated jaws, but I removed the one against the roll pin. Since they are plastic, it did not mar the lower, but provided plenty of power to push the pins. Only other thing was installing the hammer. I lined up the holes and inserted a small punch which helped when setting the Hammer pin. Better than trying to push the hammer down with one hand and trying to set the pin.

      February 23, 2021 7:37 pm
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      Michael Higgins

      I've used this for 3 lowers. Works perfectly every time. USE a plastic hammer head. Thanks Eric!!!

      January 30, 2021 10:47 am
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      Enos Bacon

      Best step-by-step I’ve seen. Well written, fully inclusive, and insightful. Thank you for sharing. I highly recommend it to anyone looking to build an AR-15.

      January 3, 2021 3:18 pm
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      Steve From SC

      Great help! Just built my first AR pistol! Had a bugger of a time getting the hammer retainer pin through but not your fault. My only confusion was the install of the buffer retainer. It isn’t shown well in the photo and I had to look around a while and zoom in on a subsequent photo to see which way the pin cap went on the spring. But I did figure it out and it is obvious once you see how it goes. Now I plan to try it out tomorrow if there is a dry spell before or during the forecast rain. Thank you!

      December 30, 2020 5:54 pm