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Old 12-25-2016, 06:21 PM   #1
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Steel Stampings and 3D Printed Plastic

So, crazy thing to come to mind, but as I was thinking about ways that the AR-18/180 and other firearms that used a lot of stamped parts could be brought back into production, I was wondering if some of the smaller stamped steel components could be replaced with 3D printed polymer parts?

There are certainly polymers available cheap these days that would be strong enough. It might allow the stamped steel designs to come back in a modified form.

I wasn't thinking so much about receivers and such, though HK and some others have gone that route. More like "Errata" parts. But, receivers could be doable with full polymer use or with steel frames with polymer cast around them.

Have a Happy One, from NJ.

David
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Old 12-25-2016, 07:32 PM   #2
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3D printing of polymers suffers from a rather criticl flaw, granular structural weakness. For manufacturing, the greatest use of 3D printing is prototyping of parts for other manufacturing processes. 3D printing is also very slow. With injection molding you could literally make 100 parts in the time it takes to make a single 3D part; and the injection molded parts would be structurally much stronger. In an earlier age, metal stamping was THE way to make large batches of small arms precisely and cheap. These days stamping is just WAY to complex and expensive to setup for manufacture. It's a bit ironic that stamped manufacturing actually became the undoing of the AR-180. To build a factory to do precise metal stamping is very expensive. Potential customers expected Armalite/Sterling to setup manufacturing for them in the host country, and neither Armalite or Sterling had the financial or engineering expertise to facilitate that for potential customers.

CNC and investment casting and or MIM casting, and extruded receivers, are easily the most cost effective way to make small arms. Which is why you see nearly no stamped steel small arms designed post 1990.

The way to make an AR-180 receiver these days is the way Nodak Spud is doing it, from an aluminum billet or forging, then CNC machined. Upper would be made the same way it was back in the day, a steel extrusion with a welded or pinned in reunion. Smaller parts for the lower would be investment cast. Or better yet, just cut the lower to accept AR-15 fire control parts.
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Old 12-25-2016, 07:54 PM   #3
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The AR-180 was a fantastic rifle for 1965, and clearly bested the FAL in combat in Northern Ireland and Rhodesia. But it was not what you'd call a perfected design. It never got the full development that the M-16 got. It suffered (although not greatly) from some issues that were never corrected. In full auto it has reliability issues related to bolt bounce. Hammers and the last round hold open had breakage problems (which supposedly were corrected by Sterling). The stock hinge was a slick design, but it was manufactured in a very flimsy way, which Stoner corrected on the Stoner M-63.

Modern rifles like the CZ BREN 805, or the Beretta ARX are much more advanced rifles that show a good deal of AR-180 influence.
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Old 12-26-2016, 04:08 PM   #4
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Stamping was great for making large numbers of inexpensive parts.
The more you made, the cheaper the unit price.

The problem is the stamping dies are horribly expensive to make and if you're making a boutique gun like a replica of a stamped rifle, the price per unit is prohibitive.
And too, the dies do wear out and have to be replaced.

Modern lost wax casting and MIM casting are much cheaper, but still, the molds are not at all cheap, so again, the only way to keep the price per unit in hand is mass production.

Plastics are very usable for some gun parts, but printed parts are simply not up to the strength or durability needed.
It's very likely that in the future the technology will improve to the point where viable real gun parts can be printed from plastic or metal, but not yet.
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