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80% build tips

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I did not do an extensive search, and I have not seen such a thread - I think there should be one so I am going to start one.

First, routers - just because I noticed a good deal on one.

I noticed this in Amazon:

Until December 24 2017, when you spend $100 on select DEWALT products, get $25 off when shipped and sold by Amazon. Exclusions apply. See discount when items are in cart. Here's how (restrictions apply)

When I went to the page where they were selling the router that 5D Tactical recommends:

https://www.amazon.com/DEWALT-DWP611-Torque-Variable-Compact/dp/B0048EFUV8
Router Guide for Finishing 80% Lower Receivers

--

we could collect links in here to 80% build threads, and any other thread with info on such builds, and we could refer to this thread which hopefully will gather more useful tips and info on 80% builds.
 
I have finished around 15 80% lowers, however I have used a full-size milling machine to do the work. Not sure there is much I can contribute if you are going the router route.

There are a couple of things that I will say that should be universal if you want to do a top-notch job.

1) drill your fire control pins undersize and ream to size. A reamer is cheap and you will end up with proper size holes that are actually round (a drill bit does not make a round hole)

2) Do a little and measure. You can only machine something as well as you can measure it. You don't need a micrometer to do an 80% lower but you do need a set of dial or digital calipers (or know how to read a set of vernier calipers). The surface finish of the fire control cavity does not need to be perfect but even using a router it should be the correct dimensions. Do the math to figure out tool depths so you don't go too deep. Make real fine passes when you get close so if you have a tool grab or slip you dont turn your lower into a paperweight.

3) Plan on doing some fitting. I have had lots of 80% lowers that required reaming out the hole for the safety detent. Reaming out the receiver pin holes on the upper. Making adjustments to magazine catches or bolt catches. Understand that some tweaking is maybe not expected but not a thing to worry about. It's simply the nature of finishing a mechanical thing.

4) If you are painting, plan on adjusting for paint. Heavy paint can interfere with interior clearances

And just my thoughts, Consider serial numbers and identifying marks. All my 80% lowers are serial numbered (my initials and a 6 digit number starting with 00001 and going up) I want to be able to identify positively any of my firearms. The serial numbers are for my own use but establish ownership and at least some hope of getting it back if it were stolen. In my opinion, there is no reason to not have a serial number on a gun you built. I have heard the "but the guberment" argument many times which is just silly. No one but me knows what the serial numbers are and unless its stolen no one ever will. They are no less off the books with a serial number which is just there so I know when I built it and that its unequivocally mine. Plus it just adds a sense of legitimacy to them when they are seen out in the world.
 
I own the little orange Rigid router in the review link and can recommend it.
In my experience with machining using an 80%ez jig, plan on 2.5 - 3 hours and probably more on your first go around. Their claim that you can do it in an hour is reeeeeally optimistic. I've found that a large, quality drill press for the first pocket holes is 10x faster than a hand drill. It's also not as destructive to the jig after it's been used a few times.
When moving on to the router phase take really small bites. Taking time on that step saves the bit and leaves a much nicer finish. That aluminum is harder than you might think. Also, shallow passes keep the bit from vibrating loose in the collet.
I've had good luck so far with trigger pin fitment but have found selector holes needing to be massaged.
I also recommend some sort of identifying markings in case of theft even if it isn't an engraved serial number on the side. I have a raw forging (in the white) that I plan to experiment with electro etching on.
80% Lower Receiver Stencils
 
Last edited:

etrain16

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I have finished around 15 80% lowers, however I have used a full-size milling machine to do the work. Not sure there is much I can contribute if you are going the router route.

There are a couple of things that I will say that should be universal if you want to do a top-notch job.

1) drill your fire control pins undersize and ream to size. A reamer is cheap and you will end up with proper size holes that are actually round (a drill bit does not make a round hole)

2) Do a little and measure. You can only machine something as well as you can measure it. You don't need a micrometer to do an 80% lower but you do need a set of dial or digital calipers (or know how to read a set of vernier calipers). The surface finish of the fire control cavity does not need to be perfect but even using a router it should be the correct dimensions. Do the math to figure out tool depths so you don't go too deep. Make real fine passes when you get close so if you have a tool grab or slip you dont turn your lower into a paperweight.

3) Plan on doing some fitting. I have had lots of 80% lowers that required reaming out the hole for the safety detent. Reaming out the receiver pin holes on the upper. Making adjustments to magazine catches or bolt catches. Understand that some tweaking is maybe not expected but not a thing to worry about. It's simply the nature of finishing a mechanical thing.

4) If you are painting, plan on adjusting for paint. Heavy paint can interfere with interior clearances

And just my thoughts, Consider serial numbers and identifying marks. All my 80% lowers are serial numbered (my initials and a 6 digit number starting with 00001 and going up) I want to be able to identify positively any of my firearms. The serial numbers are for my own use but establish ownership and at least some hope of getting it back if it were stolen. In my opinion, there is no reason to not have a serial number on a gun you built. I have heard the "but the guberment" argument many times which is just silly. No one but me knows what the serial numbers are and unless its stolen no one ever will. They are no less off the books with a serial number which is just there so I know when I built it and that its unequivocally mine. Plus it just adds a sense of legitimacy to them when they are seen out in the world.
Not being a machinist, can you help me with the type of reamer you're referring to. When I think of a reamer, I think of a pipe/conduit reamer, which I'm sure is much different than what you're talking about.
 

Ura-Ki

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A few tips to share. When using a router, the best ones are the variable speed ones, and in use a RotoZip my self. Many of the end mill bits and other tools ate not ment for the speeds single speed routers run at. Like others have said, go slow, take small bite and measure often!
For drill press work, a good cross vice is worth it' weight in gold, spend some money here.
Top shelf drill index, the quality of bits can make of break your projects.
Hand reamers are a most have, strait and taperd in all the sizes you need.
Center punches, roll pin drifts and good sharp center punches and drivers.
Good sharp files in standard single cut and Swiss cut with file cards to clean and maintain your files. I find files to be one of my most used hand tools, it pays to have top quality files and a good maintenance regime.

For pistol building, besides the frame jig of choice, rail stones and files, scribes and machinist marking dye, large and medium single cut files, as well as medium and fine Swiss files. Small stones for hand fitting parts, and Moto tools for shaping and blending parts.
A really big and strong vice with soft jaw inserts, and a good figuring tool set for doing barrel work, and for slide work.
Any set up tools your pistol build needs, from link pin cutters, to safety sanding guides, barrel alignment jig/holding tools, ect. All will lead to good succes with your builds and will allow you to turn out nice work, and it gives you much more control of fit and finish!:)
 
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This is the router I use:
RIDGID 5.5 Amp Corded Compact Router-R24012 - The Home Depot

This is the Jig I use:
80% Arms:Universal AR-15 Easy Jig Gen 1

I can't say enough good about both. I and a couple friends have cut over 2 dozen receivers with this set up having no problems. I would like to sell my jig only because I want to upgrade to their new one that will do the 5.56, 7.62, 9mm and .45ACP receivers. There has already been some good advice here about taking it slow with small cuts, esp when getting deeper into the fire control pocket. Keep your bit lubed (I use Kerosene) and blow out the chips often. I also keep the router table of the jig lubed lightly and that helps the router glide smoothly.

Take your time.
You want to build something you can be proud of.
Follow the above and I promise you most people won't be able to tell the difference between the finish you cut with the router and one cut on a Bridgeport.
If anyone has any questions y'all can ask here or PM me and I will gladly share everything I've learned.
 
The trigger pins are .154. You need a solid carbide chucking reamer, I believe its a number 23 size.

You can use a cordless drill to run the reamer though while it is still in the jig. Use lots of oil, the hole should be drilled to the next smaller fractional size which would be 9/64 (a 5/32 is basically to size) if you only have fractional bits. If you have a number set a #25 would be a good/better choice.

While you are buying reamers you should buy a 5/64 or two which is the gas block roll pin size. It always is a good idea to assemble a gas tube and gas block and use the reamer in place prior to putting in the roll pin. It will save you all kinds of assembly headaches.
 
OP
The Heretic
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Q: Once done with the machining/etc., what does one do with the now bare metal? Home anodize? Cerakote?

The lowers I bought are coming already coated and the mag well is already broached, but cutting these pockets and drilling holes means that there will be bare metal, and as pointed out, one has to account for any coating after machining operations.
 
Any opinions on the best choice for an 80% lower? Forged? Cast? Billet? Does it make that much of a difference?
Personally, I would stay away from cast or polymer ones. Forged or billet ones are fine as long as they are 7075 (I would stay away from 6061 ones as well but that is just personal feelings) Just be aware that not all billet ones will work with all jigs. Much of the time you will have to buy a jig from the folks who offer the billet lower. All forged ones will work with all jigs.
 
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Any opinions on the best choice for an 80% lower? Forged? Cast? Billet? Does it make that much of a difference?
80% Arms:80% Lowers

The above make REALLY nice looking weapons. They offer them finished or in the white, even blems. When I'm building a weapon for me these are the ones I use. They have uppers as well, with or without FA. Other than that stay with a forged. I have bought forged ones in the white from many places and they ALL look the same. You will pay more for the Billet, but they are worth it to me in the way the finished result turns out.
 

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