Calling all AR 15 80 percent builders...NOOB with questions.

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ol' scratch

ol' scratch

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A week ago I found out a neighbor was getting rid of some reloading supplies and an 80 percent AR jig with 2 80 percent receivers and one 0 percent. I did some horse trading and now have the whole lot. I have a custom graphics idea I am floating with the lowers. My questions are-

What are some things I should be aware of while finishing these?
Any advice concerning easier ways of doing things?
I have a drill press, a vise and a full set of tungsten carbide bits. I plan on using them to finish the 80 percent receivers. Any thoughts?
Is there a place I can send the 0 percent to have it milled so it is an 80 percent so I can finish it with my jig?

Thanks for all the advice in advance. I am kind of geeked about this. I have build all my AR's, but I have never finished an 80 percent before.
 
What is the 20% that remains to be done?
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There are about 3 different types of 80% lower receivers, depending on what area remains unfinished. Some need to have the mag well machined out, some the FCG cavity, some the buffer tube threads.

Considering the price of stripped lowers, messing with an 80% receiver (IMO) is not cost-effective. (That is, unless you want to do a project for its own sake, or want to circumvent possible legal restrictions.)
 
Unless you already have the equipment, I don't think that it will be cost effective. Lower receivers are cheap. Besides, are these serial numbered parts? I really don't know what the legal ramifications will be, if they aren't.
 
Tungsten carbide bits are neither necessary, or desirable for drilling aluminum.

Your chance of snapping one off in a hole when the aluminum grabs it are much greater then with an ordinary HS steel drill bit.

rc
 
First off, I have the jig and the receivers already. That was part of the deal with the reloading equipment and the reason it is economical. I originally thought about doing this but the jigs and 80 percent receivers didn't make much sense because you can get a stripped lower cheaper. It is also legal to do this.

Thanks for the information on the bits. I will use an alternative.

These have finished mag wells, and fire control housings. They need threading for the buffer tube, pistol grip hole drilled and tapped and all holes drilled. I do have taps, but will have to purchase the large tap for the buffer tube.
 
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Is the buffer tube thread even a regular (standard Imperial) thread or is a custom tap required?
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It's a 1-3/16"-16TPI thread. A bit bigger than what's included in most tap and die sets. It'll run about $70 for the tap.
 
read online somewhere that someone used a 3D printer to create a hard plastic lower receiver for the AR15 from scratch.. sort of unrelated, but it worked well, id like to try that myself and torture test it
 
Tonyangel, I may be wrong,but I don't think the 80% lowers have serial numbers.The numbers are required when the lowers are finished,but not before.Again I could be wrong. Can anyone tell me for sure?
 
Remember the drill press well not like any side loading, drilling and plunge cuts are fine, use HSS cutters and lots of cutting fluid/coolant. Drill all your pin holes under size and finish with a reamer.

No serial # is required but I would have some unique name or number engraved for positive identification.
 
High Speed tooling is just fine for aluminum. I do it pretty often at work. The problem *sometimes* with H.S.S. tooling and aluminum is people run it too fast and it doesn't cut well. Or they don't put enough feed rate on it and it rubs away the metal rather than breaking a chip.

3.82 (constant) X 250 (Surface feet per minute for H.S.S. cutting aluminum) / tool diameter = spindle speed.
Ex: 3.82 X 250 / 1/8" drill means 7640 RPM

Carbide tooling, what a lot of machinists are used to now, would run in excess of 15,000 RPM for the same diameter drill.

Your home drill press, incapable of that speed, would require a lot less speed and a heavier chip load to keep it from cutting like crap. I like to use cutting oil rather than coolant when machining aluminum.
 
No serial number is required on any homemade firearm, unless Title II.
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I will add to this, you don't need a serial number, or manufacturer name and address unless you plan to sell it later. You can make all the legal guns you want, with no serial number for your own personal use.

You must also make the gun yourself, you can't legally buy an 80% lower and take it to the local machine shop for them to finish it out and claim you did the work, avoiding the paperwork.
 
madcratebuilder said:
Remember the drill press well not like any side loading, drilling and plunge cuts are fine, use HSS cutters and lots of cutting fluid/coolant. Drill all your pin holes under size and finish with a reamer.

No serial # is required but I would have some unique name or number engraved for positive identification.
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I wasn't going to post my ideas for graphics until the receivers were done; but what the heck? My brother is designing a middle finger with the term (fill in the blanks) ---- --- Brady Campaign. I already found someone who would engrave it for me. I will ask one of the moderators if it is HRM if it is blacked out before posting pics. I want to use one for a varmint upper and the other a mid length. I will also have the lowers serial numbered just in case they end up missing.
 
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I finished my receiver but...

I am not going to get it engraved. I did turn out pretty nice, but I botched the anodizing so I am having it Gunkoted. Somethings worked out really well, others not so much. The buffer detent is off center but the buffer threads are spot on. The receiver is functional, but was out of spec from the factory and required some filing to make the trigger components and upper fit. I am glad I did the project, however.
 
rcmodel said:
Tungsten carbide bits are neither necessary, or desirable for drilling aluminum.

Your chance of snapping one off in a hole when the aluminum grabs it are much greater then with an ordinary HS steel drill bit.

rc
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I concur, but breaking in aluminum isn't the problem. It's the threads. Aluminum requires a very sharp thread, whereas steel isn't as picky. The point at which the two lands in the thread meet must be more precise for aluminum, or what it cross thread. The same 1/2-13 thread tap for steel is not the same as the one for aluminum.

12 years in a machine shop.
 
Yhea I have a CNC mill that makes it o lot easier. BTW thanks for the welcome and nice comments.
 
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