Building it yourself... who's done it?

[UnforseenWeather]

I've assembled several AR lowers and that's not any big deal - print instructions, follow them, voila, you have a completed lower. But now I'm thinking about building my own uppers, just for myself and to my own specification.

So who's done it? Where are the best resources for info - and prices on parts?

I put this in the Armory section so anyone who's built a gun can post, not just AR or AK guys.

[4track]

LIke you, I have assembled several lowers (actually, every single AR pattern weapon that I own), as they are pretty hard to get wrong.

However, I have never built an upper, because I have always purchased them as complete assemblies.

My reason for this is because most quality manufacturers (like BCM, DD, etc.) already have something put together that is to my liking. I trust that they are assembled to specification with quality parts, and then test fired.

I would imagine that, as long as you have the proper quality parts, tools and instructions, it shouldn't be a big deal.

My friend has assembled a couple of uppers, and it seemed, to me, just as easy as doing a lower.

[Dave R]

I can't contribute much to this topic, but if you run into any specific problems or questions let me know, I have a buddy that builds and sells custom ARs; I can ask him and get back to you.

[waffenmacht]

I have probably built 80-100 AR's in the last few years. Rarely a day goes by that I'm not turning wrenches on some type of military firearm. Nowadays I mostly do Cerakote refinishing...which entails a complete teardown and reassembly. There are trick with AR's that you just don't learn from books, spec sheets, or a first time build. Having the right specialized tools for the job and experience using those tools makes all the difference. I repair quite a few rifles that have been damaged from first-time builders. Now don't let that discourage you, the only way to learn is to get in there and get dirty. Stay with true mil-spec parts and avoid anything that's "new and improved". Look at builds that have thousands...not hundreds of rounds through them. Look at builds that see 1,000 rounds a day without cleaning. That's where differences between hobby guns and work guns become apparent. If you have any specific questions..feel free to ask. I'll try to steer you in the right direction depending on your needs for the rifle. That being said, today there are excellent factory guns priced so cheap you really can build a quality rifle for what they sell for. Colt's can be had for $850, as can BCM's and LMT's (LMT's are a little harder to find but they are out there).

[Diz]

Building an AR is like building anything else. It looks appallingly simple in theory, but once you get into it, having the right tools, and some experience come into play. Waffenmacht pretty much laid it out. I don't know if I've built (or torn down) as many as he has, but I've done a few. And like him, I am primarily into finishing these days, although I still play with KG Gunkote, and occasionally Duracoat.

Here are a few take-aways. To really do it right, you need the proper tooling. Investing in the proper tooling makes all the difference between a good and a so-so build. The problem being that you can spend nearly as much as a nice rifle costs to get tooled-up, so if you're only building one or two, it's really not cost-effective. But if you plan on doing this as a side business in a barter economy (good idea) then by all means, get the right tools for the job.

First of all, you need to be able to torque the bbl to the upper properly. To really do this right, you need a block to hold the upper in your vise (as opposed to bbl blocks), and a GOOD (not cheap) wrench (that fits your bbl nut pattern) and torque wrench. My experience has been that due to mfg tolerances, getting the notches to line up for the gas tube oftentimes means choosing between a much lower setting or going up much higher. Since the path of least resistance is going lower, a lot of guys choose to do this, with resulting problems. So key point, always torque the bbl nut HIGHER if necessary to line up the notches. And with aluminum, it pays to go up and release at least three times, to "set" the parts, before final torqueing. I think this is covered in the mil-spec manual but bears repeating. And use a good grease (anti-sieze compound) to keep the aluminum from galling. Lots of guys don't, and this affects the torque value as well.

Another point. Make sure the FSB is perfectly aligned with the upper. You'd be surprised. Some bbl pins are slightly off, some uppers have a little play in the notch. Be sure you fine tune this before final torqueing. Have not seen a lot of this lately, due to the higher quality components now available. Like 4-trk said, stick to quality components, mil-spec or better, for fewer head-aches. I used to turn the vise and sight in on a zeroing target on the wall to make sure.

The AR does not have an adjustable headspace, per se, but I'd still check it after torqueing to make sure you're in spec. Again haven't seen this as a problem lately, but always check it anyway. If the headspace is off, it can be fixed, but I would recommend just switching out parts (usually upper) until they fit. This means you need at least, Go and NO-GO gages.

If you can get this part right, you're half-way there. A lot of guys mickey-mouse their set up, using cheap tools, and this will sometimes bite you in the ass. Good tools, solid bbl torque, will get you set up with a solid foundation.

Gas tube. Again deceptively simple. Be careful not to over-tweak it when installing. Try twisting slightly instead. Make sure the bolt carrier will free fall onto it, by gravity only. Use a long pin punch on a piece of tubing to make slight adjustments if necessary (as opposed to just tweaking it with a screw driver). Every time I replace the gas tube, I use a new roll pin. This will ensure you minimize gas leak.

Next is building the BCG. Again start with good components. Torque and STAKE the gas carrier key way screws. Yes, it's just as important as they say. Use a M-16 carrier. Use a M-16 firing pin. Get a good bolt. Use the extra HD extractor spring and o-ring if you have a 14.5" or less bbl.

This is all done for you by BCM and others. That's why it's easier to just buy the upper these days. But, there may come a time when it's not.

The lower is pretty standard assembly stuff. More guys have done this part, obviously. But again, tools make a big difference. Yes, you can assemble it on your kitchen table. And you may have to some day. But for now, get a mag block holder for the vice. Get the right pin-punches, as in good quality from Brownells, not junk from "Northern Tool" or whatever. Get the little pin that compresses the forward pivot detent spring, and has a hole in it to pass the detent through. Get it now and save yourself a lot of aggravation. If you're not vise-mounted, get the delrin block from Brownells to rest your lower on when driving pins. Get a nice rawhide mallet for driving pins, vice your claw hammer in the garage. Use a prick punch (or make your own from an extra pin punch) to finish set your pins. The cone-shaped point will self-center in the roll pins, helping to prevent slide offs, and marring the finish. It will also slightly expand the roll pin for a perfect fit into the hole, with the angle of the grind setting the depth you want the pin bellow flush. Nice professional touch.

I prefer standard LPK's. CMMG makes one of the best out there. Use the rawhide mallet to set the hammer and trigger pins.

On the buffer tube. Always stake the collar. Yes, it's just as important as they say. Again a pin punch ground to the right angle works great here, if you don't have the fancy colt square tool. Prick punch it approx. 1/3 of the thickness of the plate, towards the collar. Progressively work the divot deeper, until enough material is displaced to enter the collar notch and prevent rotation. Start back deeper than you think is required. If you run out of material before it displaces into the notch, you'll get a "break out". But no big deal, end plates are cheap, get a few extra and practice. Watch the alignment of the bottom latch detent holes. Depending on tolerances, the whole buffer tube can twist slightly as you torque the collar down, making the butt stock slightly twisted in relation to the lower. Unless you're the Hunchback of Notre Dame, keep this straight.

I keep a bunch of springs, and detents, and roll pins on hand. Depending on use, but at least annually, do an overhaul. Springs wear out. Replace them on regular basis and make your life much easier. Especially the recoil spring. Keep a new one on hand and measure how much your old one shrunk. More than an inch shorter? Replace it. Rebuild the bolt frequently. New ejector and extractor springs make a huge difference in weapon's reliability. My bud tells me their M-4's get professionally re-built by civilian contractors before each deployment. Use that as a guide.

[waffenmacht]

The only two things I can add to Diz' post is: The correct (per spec) grease for a barrel nut is Aeroshell 33. If you know and aircraft mechanic, he can get it. A little goes a LONG way. Also, when barrelling an upper, a reaction rod is the way to go. It will allow you to rebarrel uppers with short barrels or long free-float forearms. Having 3 different reaction rods, I rarely ever reach for the vise blocks anymore.

[4track]

Jan 5, 2015 10:21:23 GMT -5 Diz said:

...Get the little pin that compresses the forward pivot detent spring, and has a hole in it to pass the detent through. Get it now and save yourself a lot of aggravation...

Do you have a link for one of these?

[waffenmacht]

Here's the one I have:

Brownell;s Pivot Pin install tool



Not the exact one I have but it's similar and less expensive:

PKFirearms pivot pin install tool


Here's another

[Diz]

Yeah seriously, that little dude will save you tons of aggravation, and lost detents! After working twenty years without one I finally got one awhile back. Don't wait as long as I did. Buy it now! Brownell's is good, so is the old Bushmaster one.

[odgreen]

You can also use a 1/4" Clevis pin to install the front pivot pin. These can be obtained at any Home Depot, Lowes, or hardware store for just under $1.00.