My AR Lower receiver from scratch

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    Beware of Dog
    MDS Supporter
    Mar 16, 2013
    4,501
    AA Co
    Possibly for manufacturing reasons if it doesn't negatively affect anything. Your front block, the well that holds the pivot pin part of the upper, is impossible to machine as drawn unless you have an EDM. You can't make square interior corners w/ a finite diameter endmill. You can get one edge square, but another will be rounded.

    Another spot this is done on commercial lowers: the buffer hole threading. It doesn't need to extend past the buffer retaining pin (its as far as you can screw on the buffer tube.) Its easy to only thread it that far when thread milling. But using a tap the threads will extend all the way across the back of the upper. Doesn't hurt anything. You can see that mega probably tapped it. Noveske thread milled it.
    Yes, noted all the perfectly square corners on the pocket as illustrated, I will amend that in my edits to reflect a 1/8" radius when milling as we do on standard lowers.

    We used a thread mill on the CNC lowers we did and we still milled it all the way...LMAO It does look a bit better stopped just short of the pocket though, imo...

    I'm thinking I will stop that cut a bit short of breaking through. As long as the corner of mating plate has no interference, it can be partially milled to clear that corner, but not all the way across the magwell front insert.
     

    chsnprodigy

    Active Member
    Dec 24, 2012
    128
    Sorry people, been busy with stuff....Im still planning on firing it at posting....I know I know...its been a while.
     

    chsnprodigy

    Active Member
    Dec 24, 2012
    128
    Finaly fired!

    OK, I know its been a while since my last post, but I finaly had a free day with nothing to do so I went to Free State Gun range in Middle River and tested my lower reciever. The people there are extreamly nice and I appreciated thier suggestions when test firing my lower for the first time. So when I got there and inspected my AR the first thing that I noticed was that my magnet for the fire selector had fallen off, guess the adhesive I used wasnt stron enough. So I wasnt able to hold the fire selector switch in "safe", but "fire" still had the magnet so that was good. Once on the range one of the employees at Free State suggested that I only load one round in the magazine, just incase for some odd reason it went full auto....this is a prototype. So I loaded one round in the magazine, fed it into the lower, pulled the bolt back, selector on fire, pulled the trigger and.....bang! Worked like a champ. I brought two different types of magazines to see if it made a difference. I brought a magpul pmag and a steel magazine. The lower didnt like how the steel magazine fed for some reason. I attempted to figure out the problem, but the lower still didnt like it. The magpul pmag had no problem feeding it. So I got brave and loaded three rounds into the magazine.....remember this is a prototype, safety first. I still wanted to make sure everything stayed where it was supposed to, and I had no safety issues. So I loaded the magazine with three rounds, pulled the tigger and the first two went off without a hitch, when the third round champberd my fire selector switch fell out....yes out. I simply pushed it back into the reciever and kept going...third shot fired. So after this I figured to load 10 rounds, all ten went off with out a hitch. So at the end of the day I fired 60 round through my prototype lower reciever without one hang up or misfire.
     
    Last edited:

    chsnprodigy

    Active Member
    Dec 24, 2012
    128
    Nice! Been watching this post for a while wondering how well it worked. Really good idea for a DIY lower

    Thanks for the compliments. Does anyone know how to attach a video? I took a video of it firing with my iphone....but it doesnt like this forum or something....
     

    Kingjamez

    Gun Builder
    Oct 22, 2009
    2,042
    Fairfax, VA
    Thanks for the compliments. Does anyone know how to attach a video? I took a video of it firing with my iphone....but it doesnt like this forum or something....

    Put it on YouTube, use the yt (in brackets) codes to link to it.

    Quote this message to see details of how I did attached the below video.

     

    campns

    Ultimate Member
    Mar 6, 2013
    1,191
    Germantown, MD
    Yes, noted all the perfectly square corners on the pocket as illustrated, I will amend that in my edits to reflect a 1/8" radius when milling as we do on standard lowers.

    We used a thread mill on the CNC lowers we did and we still milled it all the way...LMAO It does look a bit better stopped just short of the pocket though, imo...

    I'm thinking I will stop that cut a bit short of breaking through. As long as the corner of mating plate has no interference, it can be partially milled to clear that corner, but not all the way across the magwell front insert.

    Any one model in and figure out how to incorporate the bolt stop?
     

    chsnprodigy

    Active Member
    Dec 24, 2012
    128
    Any one model in and figure out how to incorporate the bolt stop?

    pitpawten thanks for embeding the video!

    As far as how to incorporate a bolt stop, the only way I can think of is to increase the wall thickness of the part the bolt catch goes on.
     

    chsnprodigy

    Active Member
    Dec 24, 2012
    128
    Loved watching the video. This is a great project, I love the outside the box thinking! Great work.

    -Jim


    Thanks Kingjamez, keep up the good work on your lowers. I must say the lower in your profile pic is one of the sharpest ive seen.
     

    kalister1

    R.I.P.
    May 16, 2008
    4,814
    Pasadena Maryland
    I have a couple questions about two of the pieces?

    On the receiver gpoo0rip part; No dimensions are given for the part that gets drilled for the grip. I see the 30 degree, but no dimension to cut it back to? The .2880 and 1.650 define the outline, but how far back to cut it?

    On the side plates that get the 2 holes for the trigger group reamed. I see a .3770 and a .3140 for the Y, but no X?

    The drawings I have are dated March 2002 Rev A for the side plates and Dec 2002 rev A for the receiver grip.

    Thank you for posting this!
     

    chsnprodigy

    Active Member
    Dec 24, 2012
    128
    I have a couple questions about two of the pieces?

    On the receiver gpoo0rip part; No dimensions are given for the part that gets drilled for the grip. I see the 30 degree, but no dimension to cut it back to? The .2880 and 1.650 define the outline, but how far back to cut it?

    On the side plates that get the 2 holes for the trigger group reamed. I see a .3770 and a .3140 for the Y, but no X?

    The drawings I have are dated March 2002 Rev A for the side plates and Dec 2002 rev A for the receiver grip.

    Thank you for posting this!

    Kalister,
    Just a heads up you will have to print the blueprints out and look at them all. A lot of the other drawings have dimensions on them to other drawings. I had to do this. There will appear to be dimensions missing, but if you take a step back and look at the other blueprints you will find the demension needed.

    As far as the dimension for the grip cut back. All I did was measure up from the bottom .288 and scribe a line, then over 1.650 and scribe a line. I then connected the two points with a scribe and straight edge. This will get you "close enough" to the required angle.

    For the plate that holds the trigger group. Yes I agree with you. What I had to do is I went back to the origianal colt blueprint (I attached it on my first post) and had to calculate the dimensions required. If I wasnt at work I would be able to give you the dimensions your looking for.....I wrote them down for future reference.

    If you have any other questions, feel free to ask! Good luck! And trust me, after building this your parts do not need to be spot on. I mislocated 3 of the side plate holes and it brought he plate up about .010...and it still works great.
     

    kalister1

    R.I.P.
    May 16, 2008
    4,814
    Pasadena Maryland
    Kalister,
    Just a heads up you will have to print the blueprints out and look at them all. A lot of the other drawings have dimensions on them to other drawings. I had to do this. There will appear to be dimensions missing, but if you take a step back and look at the other blueprints you will find the dimension needed.

    As far as the dimension for the grip cut back. All I did was measure up from the bottom .288 and scribe a line, then over 1.650 and scribe a line. I then connected the two points with a scribe and straight edge. This will get you "close enough" to the required angle.

    For the plate that holds the trigger group. Yes I agree with you. What I had to do is I went back to the original colt blueprint (I attached it on my first post) and had to calculate the dimensions required. If I wasn't at work I would be able to give you the dimensions your looking for.....I wrote them down for future reference.

    If you have any other questions, feel free to ask! Good luck! And trust me, after building this your parts do not need to be spot on. I mislocated 3 of the side plate holes and it brought he plate up about .010...and it still works great.

    Thanks, I looked at the colt blue print for the dimensions and scribed the line for the grip piece. Almost there. Those were the only issues i could not define from the prints. Great job. Thanks again!
     

    chsnprodigy

    Active Member
    Dec 24, 2012
    128
    Thanks, I looked at the colt blue print for the dimensions and scribed the line for the grip piece. Almost there. Those were the only issues i could not define from the prints. Great job. Thanks again!

    Those should only be the only "problems" you'll run into. Good luck, keep us posted.
     

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