AR-15 lower - 0% - build from billet

[xaerorazor]

Good Day,
I may be new around here, but I'll be posting my progress on building an AR-15 lower from a piece of 7075-O Aluminum billet.

I have managed to get some 7075-O Billet on the cheap so i decided to build something from it. So I got myself some blueprints and am working on it. I'll add photos as I go.

My current progress:
Convert drawings into a Solidworks file.
2014-06-29
I needed to plan out how I will be milling it, so I have Solidworks available to me, which is great for planning on how to mill a piece of metal. I'm about 1/3 done with the model so far, I have one side left then to create the step by step sheets to build it.
2014-07-01
Model is done, about to make the step by step drawings....
2014-07-07
Project on hold due to billet issues...
2014-07-08
Project back on, going to do it on the -O after doing some research.
2014-07-20
I finally started machining, starting off on facing. Also did some measuring, and I have enough for a upper, also found out that a new instrument being built at work needs to be heat treated (also in 7075-o right now, metal was ordered wrong, but still needed to work on it), so I'll be slipping it in the shipment, their not charging me by the lb. So I'm happy to be getting a free up to -t6.

If anyone has any ideas or tips, please jot them down for me, and for others.

[kcstott]

Why don't you go over to CNCgunsmithing and download his solidworks file or the Iges?? Save you some work

[xfer42]

I was going to try that, but I found that the 0% 7075 forging($20 @ rguns) was less $$$ than the huge block required. So it didn't make sense for my purpose.

[xaerorazor]

Why don't you go over to CNCgunsmithing and download his solidworks file or the Iges?? Save you some work

I did get those files, and I'm using them to generate a new model. I kept having problems with feature ident on the models he has up, plus what features it did manage to ident were out of order and made no sense for milling by hand (i dont have a cnc/cam mill).

[xaerorazor]

I was going to try that, but I found that the 0% 7075 forging($20 @ rguns) was less $$$ than the huge block required. So it didn't make sense for my purpose.

Picked up a scrap billet piece for $10, just happened to be the right size. Never know what you might find at a scrap sale.

[bksa]

The 0% forgings do not let you build a custom billet with your own designs. You're limited to the standard milspec lookalike billet only.

e.g. integrated trigger guard for one.

I've milled out a lower from acrylic as practice, fun but time consuming for sure. I wouldn't even think about it without a CNC mill.

[kcstott]

I have not read of anyone finishing a % anything completely at home on a manual mill, accept for me I'm sure there are a few out there.
I thought about a billet but decided to use a forging and save any billet attempt for a AR10.

With all the AK parts kits out there and TM releasing there 1911 Frames, AR's have taken a back seat for now.

Good luck your project

I did a 10% three years ago only the mag well was broached. A month of sundays with building fixtures as I went. Fun though for sure and now there ain't a feature on the ar i can't get to with the mill. I can do the buffer retainer in my sleep

AR Build Not a tutorial or anything just documented my progress.
I would not do that again unless I had no other choice.

[xfer42]

The last time I made one from a 0%, I think I got it down to about 16 hours. I could shave a lot time off. Ive cleared out 8 magwells with a CNC mill, and its the most un fun part because I have to babysit it all the way through. I use G83 operations and two different 1/8 in bits. That's one part that might actually be quicker with a manual mill (minus moving to the exact coordinates, and compensating for backlash).

[kcstott]

You could hog 90% of the material out then broach the rest with a key way broach set.
I came up with this years ago

Machine two blocks of steel that will fit a finished mag well snug. Then machine the groves to support a 1/4" keyway broach for the corner radii and the other block for the tiny step and the mag catch slot.

You rough and finish the mag well except for the corners and the step. Drop in your die insert the broach, drench it in oil and shove it through. repeat three more times. then swap blocks and hit your mag catch slot.

Yes not the best way to do it but is beats trying to drill or using long thin endmills and if you design your blocks to use standard broaches tooling replacement is easy. You just need to grind a radius on the broach

[pacific_v]

If you could make an 80% billet lower patterned exactly like a Mil-spec forged lower I'd be interesting in buying 4 of them depending on the price.

[bigcalidave]

If you could make an 80% billet lower patterned exactly like a Mil-spec forged lower I'd be interesting in buying 4 of them depending on the price.

Why do you want that? What's wrong with the standard forging. You know they look that way because of how they are made, doing all those smooth rounded corners would be a nightmare to machine. If you want a lower that looks like a forging, buy a forging.

[kcstott]

If you could make an 80% billet lower patterned exactly like a Mil-spec forged lower I'd be interesting in buying 4 of them depending on the price.

CNCgunsmithing sells them and they are like $350 each

Why do you want that? What's wrong with the standard forging. You know they look that way because of how they are made, doing all those smooth rounded corners would be a nightmare to machine. If you want a lower that looks like a forging, buy a forging.

Yep lots of 3D surfacing and that takes a bunch of machine time.

[Lostsheep]

I'm pretty sure a forging is going to be stronger than a billet. Not that a billet is bad but why make something look like a forging that will take a lot of time, cost you more, and then be inferior?

I'll spend $1 for every 1% that is completed on a lower; that is a bargain.

ETA: Forgings are stronger because of how the grain boundaries follow the geometry of the part. When milling you have no choice but to cut across the grains thereby exposing more grain boundaries. In forgings the boundaries "flow" with the geometry. As all failures begin at grain boundaries it is desirable to have fewer of them intersecting the surface of your part.


Image retrieved from: http://sifco100.com/when-only-a-hammer-will-do/

[Sunday]

make the billet lower thicker.

[pacific_v]

Why do you want that? What's wrong with the standard forging. You know they look that way because of how they are made, doing all those smooth rounded corners would be a nightmare to machine. If you want a lower that looks like a forging, buy a forging.

I've seen one done before and it looked beautifull. Also with a billet lower everything would be a lot more true and without any variance of being off by a thou or two in certain areas, or also wouldn't have little nicks, dings, etc etc.