Saturday, November 24, 2012

Building an AK47.........from a shovel?

Okay, I will admit to earning my moniker a million times over.
I've had plenty of friends give me the hairy eyeball for some of the things I have cobbled together in my lifetime.
Plenty of people looked at me like I was out of my mind when I said I wanted to build a rifle, specifically a .50
When I told Eric at Bacon Fat Labs I was going to make a firing pin out of the shaft from an old shock absorber, he offered to pay for some 4140 round stock out of his pocket.
KX59 still regales me with tales of his own head scratching over my ability to remove a broken, cross threaded screw from the bolt of my .50 in the field using nothing more than my Gerber multi-tool.
I've found uses for duct tape and coat hangers that would make a Khyber Pass native shake his head and walk away.
I've done paint jobs on different things that would make Earl Scheib cry.

In my time on this earth, I've done some pretty insane things, but never, ever, ever, have I looked at a shovel covered in manure and thought to build an AK receiver out of said manure shovel.

Somewhere, Mikhail Kalashnikov is now toasting this man's success with a bottle of vodka and is developing a flinch all at the same time.

I bow to his resourcefulness. I have been one-upped, and I can think of no way to top  that.
The Redneck Engineer is no longer the lowest common denominator when it comes to scrap yard gun building. I now hang my head in shame, and walk away salaaming to the builder's awesomeness.

This man will now live a life of dancing and song while having various women thrown at him, all the while living in Massachusetts.

Monday, November 19, 2012

Building the 0% AR15 forging

In this nice little world we live in, there are two types of things that matter.
1. Guns
2. Everything else.

Well, to our friends at the BATFE, that's how it's all grouped, and there's a lot of stuff under the "Guns" portion that we here at this blog are interested in. Likewise, there's lots under the "Everything else" header that pertains to this blog. I know what you're thinking, what on earth is this redneck babbling about, and why should I care?
Keep reading. We're getting there.

Repeat visitors to this blog may have read a time or two that I've mentioned something being "80%" done, or an 80% kit, etc. This generally means is in reference to the BATFE's ruling that a gun ain't a gun if it ain't up to the 80% completed mark. The 80% that matters isn't just the whole receiver, but the parts that make it accept a bolt, a magazine, and a trigger group. You can drill holes in a block of aluminum until it turns to dust, but it ain't a gun until it accepts all of the above.
Now, go back to what I said up top......
It either is a gun, or it ain't.

This is a gun.

This is not a gun.

If THAT ain't a gun, then this damn sure ain't a gun, either.

Now, what does all of this have to do with this blog post?

Simple. A while back at the beginning of the year, I bought a bunch of the 0% AR15 forgings as shown in the last picture there. There is not a single bit of machine work done to these prior to you buying one, it's the same forging that almost every AR manufacturer in the US uses. Yeah, I know, so many of them claim they build their own proprietary design on their in-house CNC machines.
They don't.
They buy these forgings, pop 'em in their CNC machine, and carve out all the important parts.
Now, some places DO build their own from the ground up, but they are usually cut from a billet of auminum, aka a big chunk of raw 7075 aluminum. There's no real advantage to one over the other, in my opinion, having fired both in several calibers.
The aluminum could not be reached for comment, either.

So, we've established that we have some castings, and that they are not guns. What do we do next?
Well, as I've been doing with raw materials since I started this blog, we turn raw materials into guns!

Full instructions on how to machine one of these castings into a firearm can be found over at Ray-Vin's site here.
I machined a couple using those plans, and while it worked great, it took a long time because of all the set up work in order to machine everything perfectly.
Enter into the picture a company called CNCGUNS, who makes a jig for holding 80% AR lowers while you finish machining them. This jig appealed to me, and even though many people advise against using it on the 0% forgings, I had to try one out.
I borrowed my jig from another homebuilder a bit back, and found out why no one uses 'em to machine the 0% forgings. You have to have the top surface of the forging completely milled to spec before you can align the jig to the receiver. Okay, no big deal, it's gotta be done anyway, right?
So, here is a forging with the "deck" machined.
 Notice that there is no other machining done other than the top and buffer are being milled free of forging flash, and the front pivot pin is drilled.
(Yes, I wear latex gloves when doing machine work. I hate getting metal slivers in my hands, and the nature of my job demands that my hands stay as oil and grease free as possible.)

Now, we can align our forging into a CNCGUNS jig.

Using a flat surface, align the top of the forging with the top of the jig, and the rear of the buffer tube area with the back of the jig.
Normally, the CNCGuns jig is only used to hold the jig in place while the FCG pocket is milled out, and the corresponding holes are drilled in the side. This is a side benefit of the jig, as I will indeed use it to do that. Having the holes for the trigger, hammer, safety, takedown pins, etc. already lined up is very, very nice and saves a LOT of setup time (as in hours of time, not minutes).
What else do I do with this jig?
Well, I can now within a matter of seconds have my forging completely aligned square to the milling table, so drilling and boring the buffer tube hole no longer takes half an hour to set up and align. I can also mill the bottom side of the forging, where the trigger guard goes, and the pistol grip area. These areas used to require a specialized jig I machined, and the forging had to be precisely clamped to a series of fixtures so each area could be properly machined.
After all, the only thing about the AR forgings that does not get milled is the side profile. Everything else gets milled to size.

One thing that was taking a very long time to setup and perform the machine work on was the magazine well and the FCG pocket. There are several holes that must be very accurately drilled to remove a good bit of material before any milling takes place, and it requires the forging to be accurately setup. Once setup, the holes must be drilled out carefully, as you are drilling them with a long 1/8" drill bit. Any excess pressure on the bit causes it to flex, ruining the hole and making the bit wander off center.
I figured out that I could make my own jig that bolts to the CNCGuns jig, and has all of the important holes already laid out, and it holds the drill bit perfectly straight while I drill. 
Using a piece of 6061 1x3 aluminum billet, I laid out where each hole needed to be, then drilled it on my milling machine.
The jig after being bolted on top of the CNCGuns jig......

The forging after the drilling jig was removed......

The forging after the holes were all drilled to their final size prior to milling....

The magazine well is now milled out, as is the FCG pocket. All that remains is the milling for the small pocket that houses the take-down pin, and as you can see, those holes are already drilled.

Once I have those pockets machined and sanded smooth, I move on to drilling the buffer tube hole and tapping it with a tap I made a while back, then I drill all the necessary holes in the receiver and finish milling everything on the outside of the receiver.
All that remains is to file and sand on the magazine well until a magazine fits, then mill the bolt hold open slot (I forgot to do that when milling the mag well) and drill the hole for the buffer detent pin.

Not bad for a 20 dollar paperweight, eh?

That's my latest project, and while this particular receiver is actually for a .45 acp carbine I'm building, I have a couple more posts coming up on this same subject.
And for those of you following along about certain drum related items, yes, I know you want me to finish the drums. For what it's worth, the drum is on a welding jig with a newly made magazine, ready for assembly and testing. That's my next build post.....

Anyway, hope you enjoyed the AR forging post.
More as I get to it........