Wednesday, December 30, 2015

Home Depot Lower, PART 2: Components & Tools

More or less finished.
A method to expeditiously build AR lowers in bulk with common tools from the local hardware store.  ...and I needed a legal throw-away lower that could be built when ever I visit that other part of the US that ain't Texas and just ship the upper to and from home.  AND the more AR15's in the hands of the general populace the merrier, I daresay!  I'd be pretty thrilled if an Australian biker gang or Ukrainian resistance group saw this and started mass producing these or something; or maybe Three Percenters could air drop these lowers into enemy territory such as Newyork and California - that'd be pretty dope!

Components and tools:
This particular specimen was not as cheap as I hoped.  The next one will be, but again, this was just a proof-of-concept.  Here is a quick rundown of components and tools used:

AR Upper Receiver Vice
  • Aluminum or steel bar stock.  Max Height: 1.50" Thickness: 1/8" - 1/4".  I used 1.50" x 1/8" aluminum stuff from the metal stock section at Tractor Supply.  There's probably better stuff to use, but this worked for me since I didn't need to do any additional cutting except cutting the length.
  • AR upper receiver vice fixture - $20 - This fixture is intended so you can affix your upper receiver onto it and clamp it into a vice to do some wrench work.  I used it as a drill centering tool to drill the takedown pin holes onto the side plates.  Only buy this if you don't have an AR15 drill press jig (or you don't want to spend $80 on one).  Alternatively you could just use the upper itself as a template to drill the holes onto the plates but run the risk of egging out the holes of the upper.  To avoid that, you can use 0.250" OD, 1/8" ID steel tubing inserted into the upper's takedown holes, clamp that to your sideplates, and use a 1/8" drill to drill out the pilot holes.
  • AR FCG "testing jig" - $18 - Honestly, only buy this with the above fixture if you're just trying
    Challenge accepted!
    to build a single AR15 lower receiver and don't want to spend $80 on the jig below.  Also make sure that this "FCG testing jig" has the hole for the rear takedown pin so you can align it to your sideplates.  If you already own an AR15 drilling fixture like this then you can just drill the axis-pin holes onto your sideplates (though I don't like the idea that if you mess up a hole you've ruined the whole plate).  There was an amusing disclaimer on this manufacturer's ebay page how this isn't a gun and that it can't be modified to be used in a gun - I like a challenge.  I wouldn't pay more than $20 for this thing, but even that is still way too much for my intended purpose.  I've been told that you can make an AR fcg trigger pack like this using 0.5" internal width square tubing. 
  • AR-15 Drill press Jig - $80 - If you've already been making making AR lowers from 80% paperweights then great, you should already have one of these by now.  If you're just trying to build a one-off AR15 lower receiver, I recommend just buying the two items above instead of this.
  • AR15 Template - $0 - If you're really just a cheap bastard, it would be great if someone made a 1:1 printable template that you could glue onto the sideplates to locate the holes and start drilling away.  I don't know if such a thing exists, but I think you could make one from the many blueprints of AR15s that are out there.  I will look into this later.
    Bastards jacked the price after my purchase!
  • Buffer tube QD sling adapter - $2.70 - I really should do a separate post on threaded buffer towers.  There are many out there and they can range from $20 - $60 which is going way over my intended budget, but you basically need a way to attach a threaded buffertube to your sideplates and this method was quick, dirty, and cheapest.  This buffer tube sling adapter has a cupped space to put a buffer tube lock ring (which run at $3-5).  I used two lock rings - one inside, one outside.  Use a 1.000" wood dowel or metal tube to align the upper to the buffertube (see fig.1 below).  I then drilled and tapped two screws on the back of the QD sling adapter to the AR FCG testing jig (fig. 2 below), then two more on the side of the plates into the QD sling adapter to secure it and prevent it from tilting backwards (fig. 3 below).  It's pretty solid at that point.
  • Screws and taps - Drills, taps and screws in 6-32, 8-32, and 10-32 tpi are cheap.  Specifically buttonhead, socket cap screws which should cost roughly $8 per 100 pack.  I suggest you buy 100 packs of all three sizes since they're cheap and handy for other projects, such as AK47s (just how my good buddy Mike Kalashnikov intended).  Probably go with the 1/2" or 3/4" length so you can just cut them down later if you need to.  For the taps, this is the only area where I suggest you do NOT buy Chinese.  Every Chinese tap set I've seen are made of super soft steel.  You can't go wrong with Irwin or Hanson taps, which pretty much every Home Depot and Lowe's sells.
Fig. 1 - Alignment of buffer tube to upper receiver
Fig. 2 - Buffer tube to receiver, backside
Fig. 3 - Buffer tube to receiver, sideview

Optional parts:
Technically you don't need fancy stuff like grips and triggerguards, but I used an AK47 pistol grip, which I have plenty just lying around (10-pack for $4 or 5-pack of grips with FCG for $10 at Centerfire Systems are pretty good deals).  It required the purchase of a Saiga screw-on grip mount.  The trigger guard was made from chain link fence brace, which we have a bunch of left over just lying around from our Llama fence.  They're pretty easy to bend with a bench vice and a pair of pliers.  For the magazine catch, it's just a straight hole bored through and the catch is tightened on with a nut - the magazine is NOT quick detachable at this point and I have not yet found an effective way to make a cheap and fully functional magazine catch (and I didn't want to do any complex milling with my drill press).
Quicky last minute notes and outro:
The problem with the gun in my previous video was not only the magazine backing out (mag catch not grabbing - needed to add more material to the catch for more grabby-ness), but also the inside of the AR FCG testing jig was a little too tight, which caused delayed hammer releases and sluggish/weak hammer strikes.  It may be advisable to somehow trim down the inside of the FCG testing jig or perhaps trim the cylindrical axis housing of the hammer and trigger.  Also, you will have to cut the front portion of the FCG testing jig to allow the 5.56 magazine to fit (cutting might be unnecessary for pistol caliber magazines).  I did this with a dollar store hacksaw just to see if it could be done without an electric disc-cutting tool, and indeed it is doable in less than 20 minutes.

So in the end, was this cheaper than buying an 80% lower and milling that out using a jig?  It was but not by much in this specific example, however, the real point of this exercise was to be able to construct a lower quickly, using only local hardware store material, constructed with garage/home tooling (and in bulk it would have been way cheaper in the long run using appropriate shortcuts), and for the most part that was accomplished.  You wouldn't even need the vices and jigs to do this, but you would need to have some kind of printable 1:1 sized template to locate the holes.  The buffertube tower seems like a major roadblock in accomplishing this build in that I had to purchase an actual gunpart - albeit a non-regulated part that can be ordered from Hong Kong, but I'm not aware of any country that would get you in trouble for ordering something minor like that.  As for the FCG being unavailable in your country, a group called FossCad has managed to 3d print an AR FCG (vid here) so I'm thinking that should not be a problem if you have access to a printer.

Related Links:
Home Depot Lower - Part 1 - Mostly rambling.
Fosscad downloadable 3d printed gunparts - The actual links to the 3d files themselves.
Vidya of testfire of my Home Depot lower.