Machining an AR15 lower receiver

Machining an AR15 lower receiver - Printable Version

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RE: Machining an AR15 lower receiver - Highpower - 06-20-2012

Meh. It will be a cake walk for you Tom.

I hear you about finding the time though. I still need to finish my 2nd and I haven't even started on the third one. Blush

Fall/winter I'll get back into the swing of things again. (Famous last words...)

I'm waiting for you to get through the barrel portion of your Stevens. I have a buddy that needs the chamber sleeved on his (original). I figured I would wait until you work out the fine details on chambering yours, to see if you run into any snags or oddities. Chin

Willie

RE: Machining an AR15 lower receiver - TomG - 06-20-2012

(06-20-2012, 05:32 PM)Highpower Wrote: I'm waiting for you to get through the barrel portion of your Stevens. I have a buddy that needs the chamber sleeved on his (original). I figured I would wait until you work out the fine details on chambering yours, to see if you run into any snags or oddities.

Willie

Willie,

There has been thinking going on about it. I've found a reasonably priced high pressure oil pump to do the gun drilling. I just need to wait until the proper sized gun drill shows up on eBay and I'll be able to drill the barrel.

I don't think chambering will be much of an issue with a .22 since the case is the same diameter as the bullet.

Tom

RE: Machining an AR15 lower receiver - ETC57 - 06-20-2012

Nice post Willie, Thumbsup

I don't believe I have ever seen the whole project from start to finish. Big Grin

Jerry.

RE: Machining an AR15 lower receiver - ScrapMetal - 06-20-2012

Darn it Willie, between you and Tom I'm not sure who I want to be when I grow up!? Tongue

Nice work on the receiver. I'd really like to get my skills to the point where I can take on a build like this some day.

If you don't mind, those forgings look nice, can you share where you sourced them from?

Thanks much,

-Ron

RE: Machining an AR15 lower receiver - Highpower - 06-20-2012

(06-20-2012, 07:30 PM)ScrapMetal Wrote: If you don't mind, those forgings look nice, can you share where you sourced them from?

Thanks much,

-Ron

Sure Ron.

Raw forgings

FYI: The price has gone up a bit since last year. I paid $29.95 for mine and I would only expect the price is going to continue to go higher in the next few months. Confused

RE: Machining an AR15 lower receiver - Highpower - 06-21-2012

Ok, back to work.
Here I am laying out the position of several corner points that are located around where the magazine well will be. I just barely touched the surface of the deck to give myself a visual indication of where each corner should be so that I dont make a mistake and accidently cut past where Im supposed to stop cutting. There is a small radius to be cut into the front of the magazine well to provide clearance for a seam on the magazines themselves. Drilling a hole down through the forging at the front of the deck leaves a perfect radius after the bulk of the metal is removed.
[Image: Mag_Well_Layout.jpg]

A series of ½ holes is drilled through to remove the majority of the metal from the mag well.
[Image: Drilling_Mag_Well.jpg]

Then plunge cutting with a larger end mill roughs out the center of the mag well.
[Image: Roughing_Magwell.jpg]

Due to the cutting forces of the mill and the fact that I was using WD-40 as a coolant/lubricant, I started to have problems with the forging starting to tip and slide down the side of angle block that it was clamped to. Jawdrop

At this point you cant put too much pressure on the holding clamps because of the now, thin walls on the sides of the mag well. I could not put any kind of support underneath the well because I had to mill completely through, top to bottom. So I dug up a scrap chunk of aluminum and drilled a hole through it. Then set it between the front pivot pin lugs and stuck a screwdriver through them to hold it in place. Blush

Setting a machinist jack out in front of the mag well bearing on my makeshift support gave me the clearance I needed for the cutter, and kept the work from moving out of position again. Smiley-dancenana

A smaller endmill was used to make the final finishing cuts on the inside walls, and bringing it closer to its final shape for holding a magazine.
[Image: Finishing_Magwell.jpg]

Unfortunately I do not own a shaper so I had to make one Rotfl

for squaring out the corners inside the mag well opening. Its just a piece of round stock with a carbide insert screwed into the end of it.
[Image: Shaper_Tool.jpg]

RE: Machining an AR15 lower receiver - Highpower - 06-21-2012

And this is the set-up. Because of a small amount of backlash in the quill splines, I needed to be able to keep the cutting tip from wandering back and forth as I worked the tool up and down with the quill feed handle. So after locking the spindle on the mill I wrapped the BRRB (Big Red Rubber Band) around the socket head cap screw and stretched it to the back of the mill. That kept the spindle splines pulled to one side effectively removing the backlash, while still allowing the quill to move up and down to let the tool cut.
[Image: Backlash_Control.jpg]

This is where my little spot circles on top of the deck come into play. The apex of the arc is where my squared corners need to be.
[Image: Corner_Broaching.jpg]

With the magazine well finished it was time to repeat the process on the rear half of the forging to hog out most of the metal for the fire control pocket. That is where the trigger, hammer, springs & pins, etc., (the inner workings) are housed. However this pocket does not go all the way through the receiver like the mag well, except for the opening for the trigger.
[Image: Hogging_FC_Pocket.jpg]

There is also a hole that must be drilled into the receiver extension threads at an angle, that houses a buffer retainer and pin.
[Image: Milling_Trigger_Slot.jpg]

There are several other steps that I didnt get pics of, but they are equally important in making the receiver functional. Drilling a couple more small holes for springs and detents. Milling slots and drilling pin holes for attaching the trigger guard plate. Drilling and tapping the hole to attach the pistol grip. And chamfering the bottom edges of the magazine well to make it easier to guide the mags into the well.
[Image: Finalcuts.jpg]

Final views coming up.

RE: Machining an AR15 lower receiver - RobWilson - 06-21-2012

Cracking Willie Worthy

Very interesting project Thumbsup

RobWilson

RE: Machining an AR15 lower receiver - ScrapMetal - 06-21-2012

(06-20-2012, 09:30 PM)Highpower Wrote: Sure Ron.

Raw forgings

FYI: The price has gone up a bit since last year. I paid $29.95 for mine and I would only expect the price is going to continue to go higher in the next few months.

Thanks much. I've got a couple on order now. Big Grin

For when I grow up. Happyno

-Ron

RE: Machining an AR15 lower receiver - TomG - 06-21-2012

Supposedly, lower forgings can be purchased directly from Brass Aluminum Forging Enterprises of Ferndale, MI. for $13 each. I haven't verified this, but the link with all of the contact information is on the forum at CNCGuns.

Tom