1. Drill front and rear take-down holes. The front one is first, and you should drill it dead centre of the lug. If you are using a drill press (as I was), you can do it in one pass. If you are doing it free-hand with a hand drill, I would carefully do one side, then the other, making sure you mark the centre points with a punch so you ensure they line up.
If you are using one of Alex’s drill plates, use the supplied bolt and fasten the plate to your casting, carefully positioning everything off of the magazine catch hole. Then drill the front pivot holes dead centre of the lugs, place the supplied ¼” bolt through, then drill out the rear take-down pin holes.
In my case, I made up my own hole layout template, and it turned out to be just a hair off. This rifle is very unforgiving on hole locations, so that “hair off” pushed everything off, to the extent it would not function. In the end, I ended up using J B Weld and re-drilling. (By assembling, you can pretty much figure out how much you are off, and how much you will need to adjust once the J B Weld sets up.)
2. Drill detent holes for take down pins. The rear one is hard to get dead on. In essence you are drilling a 1” long hole free hand to intersect a ¼” diameter hole dead centre and dead centre of the casting wall thickness. It’s not that easy. I took two tries (thanks, J B Weld!) and still wound up slightly off-centre. The detent still functions, even though I was not dead on.
The front one is easier. I could not find any dimension to tell how deep to go on this one on the lower receiver drawing that I got from AR15.com, so I reasoned that if the rear one uses the same detent and the same spring, the depth of the hole should be the same. So I drilled it 1” deep, and there you go.
3. Drill hole and tap for pistol grip. I set this up in the drill press and just turned it loose. No issues here. (This was actually the second thing I did, after the magazine well.)
4. Ream hole and tap for buffer. This is the most nerve-wracking and frustrating part of the whole job. I used a 1 – 1/8” drill bit and a hand drill, with the receiver held in a vice. It chattered and caught and carried on something awful. I was convinced that I was going to end up ruining the casting before I was through. Tapping was relatively straight forward, but my comment here is that the chattering ended up causing the hole to be slightly over 1 - 1/8”. This in turn ended up causing a less-than-perfect tapping operation, with the net effect being a sloppy thread that the tube screws into. While it holds (more on that later) it is below what I would consider to be reasonable workmanship standards. If I was doing it over again, I might consider using a 1 – 1/16” drill, then testing to see if the tap would go. If it would not, at least I would have less problems getting the 1 – 1/8” drill to follow through the now-larger pilot hole. Others I have heard use a 1 – 1/8” reamer. This may work better, but I do not have any experience with this, so others can comment on that if they like. Incidentally, I believe you can rent the drill and the tap from William (and for sure you can buy them from him). I bought mine outright up here in Canada, because I have a friend in the business and he got them for me at cost, but these two items alone will run you close on $100 USD to buy from an industrial supply house.
The issue of sloppy threads turned out to not really mean all that much (other than I still don’t like sloppy work), but in the end the whole works was fixed rather neatly. The US Army manual on maintaining this rifle says that the buffer tube should be torqued to 35 to 39 foot-pounds (at least I think that’s what I remember it reading). To do this you need the special tool and a torque wrench. Since I had neither, AND I had sloppy threads to deal with (which I had my doubts about torquing up anyway), I used Loctite Red, available at any auto parts store. This worked beautifully and solved both problems. If you ever need to get it apart, you simply heat it with a propane torch to 450, and it breaks down.
Here is the assembly with the pistol grip and buffer tube / stock assembled:
4a. Drill hole for buffer retainer and spring. This was one of the steps that William’s list did not have, and it’s complicated further because the AR15.com drawing does not give you the diameter dimension (unless I just missed it). So I measured the actual part’s diameter and added 1/64” to allow it to move freely. (I seem to recall it worked out to be a 7/32” hole, but you should check to be sure before you drill.) To locate this hole, screw in the buffer tube hand-tight, then eyeball where this will have to go in order for the pin to act as a retainer for the recoil buffer, yet the buffer tube needs to act as the retainer for the shoulder of this spring-loaded retainer. The print does call for this hole to be 23/32” deep, but I doubt you need to be that critical. “Just under ¾” is the way I did it. Incidentally, if you don’t mind having to physically hold the buffer back by hand when you assemble the rifle, or remember to catch it when you disassemble your weapon, then I think you could safely forget about this step. In the photo below you can just see the retainer at the bottom of the buffer, inside the buffer tube.
5. Drill hole for trigger and hammer. These are by far the 2 most critical holes in the entire casting (and, of course the Selector hole as well which fills out the three inter-related fire control elements). I really screwed these up the first time and was too far forward by about 1/32”. This was just enough to prevent the fire control group from functioning. (And I went through the steps of actually testing the hole layout by building a test jig and pre-assembling everything first. The test worked out fine, but I forgot about one critical thing … the back wall of the magazine well.) I used the old J B Weld, adjusted and re-drilled. Second time was a charm.
With Alex’s jig there should not be an issue, since all of the pilot holes for drilling are there and you just need to do it. Just put the screw through the magazine release hole, put in the front and rear take down bolts (these all come with Alex’s plate), and then drill these two holes.
6. Drill holes for selector. Again, with Alex’s jig, just keep on rolling, but with the 3/8” drill bit this time. In my case, I had to re-do this one as well.
7. Drill hole for selector detent. This is relatively straight forward, but like the rear take down pin detent hole, make sure you start off at the correct angle to intercept the selector hole dead-center, and dead center of the casting metal as well. Otherwise your selector may not “catch” in the two positions properly.
I also think it is a good idea to go ahead and assemble the trigger, the hammer, the disconnector and the selector (including the springs) before you go any further and test them. You can find the operational tests at AR15.com in both the articles and in the manuals, but in a nut shell here is what it entails:
When the hammer is forward, it should not be possible to move the selector to safe. Manually pull the hammer all the way back until it catches on the sear. Move the selector to safe and it should now prevent the trigger from releasing. Move the selector back to fire and pull the trigger. The hammer should release forward. (Catch it with you thumb so you don’t beat your receiver to death.) Now pull the trigger all the way to the rear and hold it there. Then pull the hammer all the way back. The disconnector should catch the hammer, preventing it from moving forward. Now release the trigger. As it moves forward, the disconnector should release the hammer, allowing it to catch on the sear. Now when you pull the trigger, the hammer should release forward. (And again, catch it with your thumb.)
8. Drill hole for butt stock alignment. This was not required for the casting I received.
9. And 9a. Open up the rear receiver area for the upper receiver lug. This also applied to the front lug as well. When I went to seat the upper receiver into the lower, the upper’s lugs were just slightly wider than the openings in the lower. A little file work to remove enough metal from the lower to allow clearance was all it took.
10. Sand or file out magazine well to fit magazine. This is just careful file work. This was actually the very first thing I did on the receiver. It is simply trying your magazine and seeing where it is tight, then removing a little metal from the well with a file, then re-testing and etc. I worked it until the magazine was snug (no slop), but would still drop out. Obviously a trade-off here, so go slow.
11. Drill roll pin hole for bolt release. This is the one hole that requires a very long drill bit to do properly. And the problem with any long and thin drill bit is its tendency to break if you put too much pressure on it. I set it up in a drill press and went VERY slowly. William can sell you this bit, or you can get it from the local industrial supply house. It’s not that expensive.
12. Drill hole for bolt release detent and spring. This one is easy to locate if you use the drawings from AR15.com. Just drill to the depth shown on the drawing. I put a piece of tape around the drill bit to mark how deep I needed to go.
13. Drill roll pin hole for trigger guard. With Alex’s jig this is straight forward, since they are also on his plates, but for me I just marked this dead centre of the lugs and drilled through.
14. Drill detent hole for trigger guard. Again, using Alex’s plate makes this straight forward. In my case, I used the actual trigger guard, the rear holes, and a punch to temporarily hold the trigger guard in place so I could locate the forward detent hole. I then marked it and drilled it.
15. Mill or file top plane down to allow bolt clearance into buffer tube. This is just slow, meticulous metal removal. The trick is not to allow yourself to get carried away. I kept putting the upper on, then checking to see if the front pin would go in first, always mindful that I wanted the top of the lower to stay flat and even on both sides. I actually found that a “Mouse” sander with fine paper worked quite well, since it is small enough to get into the area, yet spreads the sanding surface enough to ensure fairly good flatness.
Finishing Up
