How to Assemble AR15 Lower - Aero Precision Lower and Parts Kit

Shoutout to Aero for including an exclusive part to hold down the rear take down pin but not the tool to actually use it

Hope youtube doesn't catch you teaching us this great video 👍

For anyone doing this for the first time, here’s my advice: buy at least one extra Aero parts/“Fix-It” kits. Once that front detent goes flying you aren’t getting it back.

The hex key he used at 9:17 for the tiny screw holding the rear spring is a .050 in case anyone was curious.

I watched another video where all the key steps were done off-camera, and the steps that were on camera were done within 5% of the edge of the camera view, or even outside the camera view. This video, on the other hand, is GLORIOUS!!! Great job, all the details, no wasted time, but good camera coverage and explanations!!! Thank you!!!

Great video, clear step by step, many thanks! 2 suggestions: I managed to lose BOTH of my takeout detent pins as they went flying off to... wherever. Managed to get replacements pretty quickly and decided not to be stupid again, so got a large box, lined it with a towel, pointed the detent and spring INTO the box as I put it in. Caught the first one before I finally managed to get it in place. Also used the credit card trick one of your other viewers mentioned below. Other suggestion: YT is gonna nab you for "how to assemble a rifle" vids. Strongly suggest you duplicate over on that competitive channel.

Aero says to cut the rear spring before adding the set screw. Made it a bit easier for me. Only had to chase and find the spring once before I cut it 😂. Thanks for the video!

At 9:42, if you have trouble pushing out the rear takedown after install, Aero Precision instructs to cut a few coils off the spring with a cable cutter. Leave it full length if you don't have a 4-40 set screw and this gets captured by the buffer lock plate

I always get the detent in with my finger then hold it down with a credit card card. Slide the pivot pin in over top of it, then pull the credit card out. Works like a charm.

this has been really helpful for me, I've never had an AR before and decided to build my own after finding a deal on a full upper assembly. Thanks for putting this series together

Doing my first AR build thank you for all the help. This was a great video.

1/4 x 2” clevis pin - about $2 at Tractor Supply. Get the one that has holes all the way down the pin. Push the clevis pin into the pivot pin hole from the left side of the lower. Align the hole in the end of the clevis pin with the pivot pin spring/detent hole. Drop your spring and detent pin through the clevis pin & into the hole in the lower. Push the detent pin in with a punch/hex key & rotate the clevis pin 90 degrees. This will hold the detent in place. Now you can perform the “switch-a-roo” maneuver as described in the video.

​@1stShotTactical I went ahead and bought a complete lower from a local gunsmith friend, but I think I'll build my 2nd AR using your video along the way. Thanks.

Patience is key. I lost my first detent. I found a 1/4 drill bit works perfectly, similarly to what he used the screw driver for(the chuck end of the bit not the drill tip). Transferring from the drill bit, that holds down the detent, to the takedown pin was super easy.

Thanks for showing these videos on putting a lower together very helpful for a lot of people to see just how to do it the right way....

A buddy of mine got me a lower and a kit for my first build. I'm only about half way since the kit is missing a detent & a roll catch. Other then that I'm having fun. I used some clear tape keep the detent pin in place while staying flexible enough to just smoosh it with the bolt thinggie. LoL. Either way it work like a charm for me. Awesome tutorial! It's loads of help. Thanks!

Awesome video!! My friend purchased a brand new upper and lower and was telling me that they’re extremely tight. When putting them together. He’s worried about it but I told him not to worry!

My lower is also aero precision. So I really appreciate you mentioning the parts that Aero specifically makes. As they were not in my kit 😂. Great video.

Where do you buy that table top AR diagram drawing?

Good step by step video sir and I used a round file to hold that front pin detent in and it worked perfectly