Choose your poison: What do you start with?

[goober]

Lots of folks want to build their own AR-style rifle/carbine/pistol. By "build" I mean actually manufacture the lower receiver themselves from a non-firearm piece of metal, not simply put finished parts together.
There have been a number of posts here with questions about how much needs to be done on this or that 80% lower, or what about these forgings, or can you do it with only these tools, etc. When that happens enough it's time for a dedicated thread or post.
This post is intended to give an overview of the spectrum of options available to the home builder, with some explanation of the amount of work to be done, tools required, skill level, and other considerations for each option. It is not intended to be an endorsement of any one product or company.

Item	Description	Tools Required	Skill Level
Stripped, finished AR lower receiver	This doesn't even qualify as "building" by my definition above, but I'm including it for reference. As a finished lower is considered a firearm, purchase must involve an FFL. All that needs to be done is installation of a lower parts kit (LPK) and its ready to mate with a stock and upper and go shoot	Punches, hex wrench or screwdriver, pliers or vise grips	Low
"80%" lower	Has just enough left to finish so that BATFE does NOT consider it a firearm. No FFL required. May be a casting, forging, or machined from billet. Generally > $100, more for specialty or custom models, or for billet (up to $300). AR15plus/Vida Rica JFMs are an example.	At least a drill press and a jig, all appropriate drill bits and taps, and tools listed above. Mill recommended	Medium
"10%" lower	Has far less than the legal limit of work done, leaving no possible chance of being ruled a firearm. These may cost $100-$300: Justin's AR10's are an example	Generally a mill, plus tooling listed above	Medium-high
"0%" forging	These are completely unfinished; a solid piece of aluminum in the shape of an AR lower with NO machining or holes. These are generally pretty cheap, < $50: DSA Item 1001 is a good example.	Mill pretty much a must, DRO a good idea, plus all above tooling	High
Billet	A solid, rectangular block of aluminum. You know what one looks like.	Generally CNC mill, manual if you are gifted	Very high, must include CNC programming or lots of manual milling experience

Now some folks will be able to finish a 0 with just files and a dremel, or an 80 with just a pocketknife (kidding) but in general the guidelines above hold true. Note that within any one category, different things may be already finished/left for the builder to do. For example on some 80's, the buffer tower hole will be drilled to 1" only, while another "brand" may have the tower drilled, tapped, and ready to attach a stock. Generally when differences exist, there are trade offs, meaning that Band A may have more done in one area while Brand B has more in another; in this way the manufacturers & vendors stay within the magic "80%" limit. Some brands may have certain work done to get one or more reference surfaces into spec as well, this helps in aligning the lower in a jig and such. Always keep in mind that while prices vary, you generally get what you pay for; if you see something advertised for $30, you can be pretty sure its not an 80.

[ferretface]

Lots of folks want to build their own AR-style rifle/carbine/pistol. By "build" I mean actually manufacture the lower receiver themselves from a non-firearm piece of metal, not simply put finished parts together.

I'm sad to say that you are 100% correct about "builders"...5 or 6 years back, I was part of the ARFCOM "Builders Squad", and built several AR and AK (as well as 45) firearms...Now the BIY Forum at ARFCOM is all parts changers...   

The only real building going on is being done in the ARFCOM/Retro Forum...

The rest of the site is tacti-crap...   

[deth502]

gotta add, YES, I KNOW YOU SAID THERE WERE EXCEPTIONS, but i gotta point one out.

i dont think it would be impossible, or even that hard to do a billet on a manual machine.

sure, it would taek ALOT longer, and you prob wont get all of the mostly cosmetic radisuses to be perfect, but giving though to propper order of operations, it shouldnt be too hard.

even though this is "cnc gunsmithing" not all of us can afford cnc   with enough practice, most procedures can be done on manual machines too.

[deth502]

btw, good explanations, this should be a sticky!!

[goober]

i dont think it would be impossible, or even that hard to do a billet on a manual machine.

point taken. these are general guidelines only, and i was referring in all cases to the tools & skills needed to produce a completely finished lower with all dimensions and profiles in spec, inside and out. some of the operations to produce such a product from a solid billet are pretty darn tricky on a manual mill. but you're right, it's possible.... i'm continually amazed at what folks pull off with minimal tooling, lots of cleverness, and great skill. the summary was kind of intended for folks just starting out, rather than the exceptional folks 

[trailblazer]

would you consider the scratch built lower a billet? that was made on a mini mill wasnt it? i forget who made it but that was a pretty nice project.

[JFettig]

I disagree on the billet requiring a cnc. Have you seen my billet lower? It could easily be done on a manual mill. Murphy from homegunsmith did one on a 3 in 1 machine.

Jon

[goober]

I disagree on the billet requiring a cnc. Have you seen my billet lower? It could easily be done on a manual mill. Murphy from homegunsmith did one on a 3 in 1 machine.

Jon

OK fine. 
I was talking in general... The target audience of this post is the 1st-time builder with little to no experience, not a trained and skillful machinist like yourself. As my attempt at a disclaimer stated, there are those that can do amazing things with very rudimentary tools. But if you're trying to decide whether to try an "80", "10", or "0" percent, you're probably not that guy. The billet concept was given as a frame of reference, as an example of the most extreme amount of machining that might be needed.
The guidelines in the OP are just that... Not the gospel. Only trying to make sense out of the options for the new guys. If you know better, then the post probably wasn't directed at you.

[Mil-Surp]

What about us guys that are molding our lowers out of carbon fiber?  You left us out 

Just kidding, nice write-up Goober.

[goober]

Heh & I forgot to put an option for pouring & casting your own as well i guess, too 
Thanks for the kind words Mil-Surp 

[Prototype Services]

I'm going to grow some this summer.

I bought the seeds off Gunbroker.....

[IOWOLF]

would you consider the scratch built lower a billet? that was made on a mini mill wasnt it? i forget who made it but that was a pretty nice project.

NO, at least not the Screwed together one, the definition of Billet is machined out of solid bar stock, IIRC.

Though, the word Billet has been Butchered over the years.