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victorgonzales
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Posted: 1/22/2013 4:02:37 PM EST
[Last Edit: 1/22/2013 4:03:22 PM EST by victorgonzales]
Is there a specific reason you can't cast an upper and lower receiver before machining rather than forging ?

Seems like the shape wouldn't be incredible difficult.
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Posted: 1/22/2013 4:04:30 PM EST
Originally Posted By victorgonzales:
Is there a specific reason you can't cast an upper and lower receiver before machining rather than forging ?

Seems like the shape wouldn't be incredible difficult.


I think shrinkage, etc would actually make it more difficult.
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victorgonzales
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Posted: 1/22/2013 4:06:25 PM EST

Originally Posted By OKSoda:
Originally Posted By victorgonzales:
Is there a specific reason you can't cast an upper and lower receiver before machining rather than forging ?

Seems like the shape wouldn't be incredible difficult.


I think shrinkage, etc would actually make it more difficult.
possibly but you could just oversize it a bit where needed I would think and the machine shop could take care of it.

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Posted: 1/22/2013 4:06:41 PM EST
It's been done. IIRC, Olympic Arms did it at one time. I forget if it was uppers, lowers, or both.
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Posted: 1/22/2013 4:06:56 PM EST
[Last Edit: 1/22/2013 4:07:40 PM EST by Torf]
Weren't the old Hesse rifles castings? Maybe I am thinking of Olympic...
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Posted: 1/22/2013 4:10:50 PM EST
[Last Edit: 1/22/2013 4:15:25 PM EST by Soylent]
Precision casting should get you a good receiver, but that is a relative term for the most part. You're going to have more problems with material properties that can be greatly affected due to seemingly minor variations in temperature, ambient humidity, etc.

While you can create precsion castings by the truck load much cheaper than you usually can other methods of obtaining your net shape, the controls to get a realible quality you will need to put into place are going to cost much more than to just use forgings and make fewer.

*ETA*
This doesn't even take into account the problems that can and will occur for machining your castings. Variations in a given batch either in ingredients or in process will cause prblems fitting castings into machining fixtures repeatably. I've worked with alot of castings from cheap grey iron sand castings to die cast aluminum for avionics trays and the like. Castings are always castings.
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Posted: 1/22/2013 4:12:17 PM EST
Olympic had cast lowers
Hesse had some fiber/polymer type uppers
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Posted: 1/22/2013 4:12:59 PM EST
Essential Arms did some really nice looking castings.
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Posted: 1/22/2013 4:13:38 PM EST
I remember lowers being cast before. I always bought forged ones.
victorgonzales
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Posted: 1/22/2013 4:14:12 PM EST
so if forgings are a bottle neck right now why aren't more places jumping into casting?
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Posted: 1/22/2013 4:15:45 PM EST

Originally Posted By shadrach:
Essential Arms did some really nice looking castings.

+2 for this. I had them. Still going strong.
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Posted: 1/22/2013 4:16:01 PM EST
Originally Posted By victorgonzales:
so if forgings are a bottle neck right now why aren't more places jumping into casting?


Start up cost and ROI basically.
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Posted: 1/22/2013 4:17:43 PM EST
[Last Edit: 1/22/2013 4:20:18 PM EST by RocketmanOU]
Castable alloys aren't nearly as strong as forged alloys. You need 7075-T6 for the current design. If you went with a casting, you'd have to redesign the buffer thread area to reduce the stress. That said, our ability to do precision casting has come along greatly, but doing complicated parts takes a lot of die design to make sure you get a good, even flow of the material into the casting cavity

ETA: There are one or two alloys that nearly compare to 7075 in strength after a temper, but they're not very common.
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Posted: 1/22/2013 4:18:57 PM EST
Originally Posted By greybear:

Originally Posted By shadrach:
Essential Arms did some really nice looking castings.

+2 for this. I had them. Still going strong.


Yep, nice preban ones too
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Posted: 1/22/2013 4:19:02 PM EST
i dont see why a polymer lower that is strengthen somehow with other materials ( not 3d printed ). cav arms did it , why has that not come back or being looked at? I would think Magpul would figure it out and make a great polymer lower
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Posted: 1/22/2013 4:23:50 PM EST
Originally Posted By Soylent:
Precision casting should get you a good receiver, but that is a relative term for the most part. You're going to have more problems with material properties that can be greatly affected due to seemingly minor variations in temperature, ambient humidity, etc.

While you can create precsion castings by the truck load much cheaper than you usually can other methods of obtaining your net shape, the controls to get a realible quality you will need to put into place are going to cost much more than to just use forgings and make fewer.

*ETA*
This doesn't even take into account the problems that can and will occur for machining your castings. Variations in a given batch either in ingredients or in process will cause prblems fitting castings into machining fixtures repeatably. I've worked with alot of castings from cheap grey iron sand castings to die cast aluminum for avionics trays and the like. Castings are always castings.


I machined investment castings for hydraulic pump internal parts. We held tolerances in the +/- .0005. They were made of bearing bronze. I think with an investment and the correct material you could be successful.
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Posted: 1/22/2013 4:28:33 PM EST
[Last Edit: 1/22/2013 4:29:46 PM EST by williewvr]
Why doesn't Magpul make lower out of plastic??


Because they are already running at max just to fill mag orders??
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Posted: 1/22/2013 4:32:38 PM EST
Originally Posted By shadrach:
Essential Arms did some really nice looking castings.


Yes. Some of them were converted to select fire and registered by Bushmaster. They called it the model J15.
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Posted: 1/22/2013 4:38:54 PM EST
The original spec was for investment castings, and the AR-15's the Air Force received were just that. I'm not positive but I believe the M16A1 I was issued in basic was a casting.
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Posted: 1/22/2013 4:43:01 PM EST
There are a zillion AR's in circulation that have cast lower receivers.

For the home shop guy, a piece of plate stock makes more sense, and doesn't saddle you with a brittle material.

Budget Casting Supply has all the supplies you'll need.

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Posted: 1/22/2013 5:04:51 PM EST
The old Essential Arms lowers were cast aluminum done for them by Ruger.

I still have my J-15 I bought from Bushmaster when they were still known as Quality Parts Corp, and it's still going strong.
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Posted: 1/22/2013 5:05:40 PM EST
You gotta remember, when Eugene Stoner designed the AR, CNC machining was a long ways off. Investment cast the receivers, then minimal machine work to finish. I believe part of the high cost of M-14's was all the manual machining on the forged steel receivers.
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Posted: 1/22/2013 5:07:39 PM EST
Originally Posted By victorgonzales:
so if forgings are a bottle neck right now why aren't more places jumping into casting?


Because forgings aren't the bottle neck.
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Posted: 1/22/2013 5:10:26 PM EST
Originally Posted By shadrach:
Essential Arms did some really nice looking castings.


A lot of those are still going strong.
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Posted: 1/22/2013 5:12:57 PM EST
Originally Posted By fishorwife:
Originally Posted By Soylent:
Precision casting should get you a good receiver, but that is a relative term for the most part. You're going to have more problems with material properties that can be greatly affected due to seemingly minor variations in temperature, ambient humidity, etc.

While you can create precsion castings by the truck load much cheaper than you usually can other methods of obtaining your net shape, the controls to get a realible quality you will need to put into place are going to cost much more than to just use forgings and make fewer.

*ETA*
This doesn't even take into account the problems that can and will occur for machining your castings. Variations in a given batch either in ingredients or in process will cause prblems fitting castings into machining fixtures repeatably. I've worked with alot of castings from cheap grey iron sand castings to die cast aluminum for avionics trays and the like. Castings are always castings.


I machined investment castings for hydraulic pump internal parts. We held tolerances in the +/- .0005. They were made of bearing bronze. I think with an investment and the correct material you could be successful.


You can, I muddied those water a little.

But, the costs of getting up to speed to get a good quality casting are going to be alot more up front and higher on an ongoing basis than just machining fogings.
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Posted: 1/22/2013 5:30:25 PM EST
Forgings are stronger than most casting primarily due to the grain structure being aligned in the forging process and the material is more dense than a casting could ever be, That being said, there is no real reason a cast receiver would not be a viable alternative to a forging especially considering that injection molded polymers have gained a following. In my business we often do mold work for die casting and permanent mold foundries, I have performed destructive testing on several casting alloys that I would stack up against a forging and not blink an eye. We have parts produced from Al-Mag, an aluminum magnesium alloy, that has great potential as a lower receiver material, especially when it is cast near net then form forged, or squeeze cast, leaving minimal amounts for machining. Investment casting is much more costly than forging, die casting or pour casting but it allows for finer detail in the casting with minimal concern for draft, undercuts or costly shell cores. Many investment cast parts are very near net shape only requiring machine work on highly critical areas.
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Posted: 1/22/2013 5:34:16 PM EST
[Last Edit: 1/22/2013 5:34:51 PM EST by Soylent]
I'm going to take a moment here and make a full confession of being racist against castings. I do know that they can be done very well indeed. But, I hates them due to some sort of weird digruntlement from early experience with lots and lots of poor quality ones. I just can't get past despising them. So, you should probably take some of my input with a grain of salt but don't dismiss it outright without running some of the costing down.
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Posted: 1/22/2013 5:44:41 PM EST
Originally Posted By victorgonzales:
so if forgings are a bottle neck right now why aren't more places jumping into casting?


Can you imagine how much money the Plum Crazy/New Frontier goofballs are making now? Maybe they will start warranty support for their original brand again.
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Posted: 1/22/2013 5:46:58 PM EST
I thought raw forgings were only 15 bucks a pop or something like that?

Would be way more expensive to create investment castings for them.


Also, because 6061 and 7075 grade aluminums don't "pour" well they usually need to add silicon to make them more fluid, which weakens them. Again you need totally different grades of aluminum to make it strong, but the properties they wanted out of 7075-T6 are no longer there.
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Posted: 1/22/2013 5:58:51 PM EST
The bottleneck is an unsustainable demand, not a shortage of anything. If manufacturers thought the current demand could be sustained they would be spending every penny they could to ramp up and meet the demand. It's not sustainable though, so no one is going to go into debt to try to meet the current demand. Couple of companies did that back in 2008 and got their asses handed to them when the market dropped out on them.
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Posted: 1/22/2013 6:05:45 PM EST
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Posted: 1/22/2013 6:09:54 PM EST
I had thought about something like this except using high performance mineral reinforced liquid urethane plastic in a 3d printed mold. I might give it a try once my 3d printer arrives
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Posted: 1/22/2013 6:33:04 PM EST
The advantage of investment casting is that you can get it pretty close to the final shape with no machining. The disadvantage is that it's not usually as strong as a forging, and it's often more expensive, though that depends on the amount of machining you save. Really an AR lower doesn't require that much strength. The weakest points are probably the buffer tube ring and threads, the front pivot pin, and trigger guard holes.

You can knock out forgings pretty quick once you've got the die. I expect that they'll get caught up on lower forgings before all that long, and machined lowers not long after that. You can machine Al pretty quick. I'm guessing that barrels and BCGs will be the bottle necks.