Re: Researching for MillenniumsEnd.com Essay

["Eric Benson" <e_r_benson@xxxxxxxxxxx>]

> The other types of construction/manufacturing for weapons seems to be
> milled/machined and stamped, which I have a very good grasp on already.
Am I
> missing any other forms of manufacture?

Casting is pretty important because it can allow complicated geometries to
be produced relatively quickly and cheaply.  Ruger, for example, uses
investment casting to produce some of the parts on the P-series pistols.
Castings can have some issues if not designed properly (the solidification
process isn't trivial), but they are a reasonable compromise when a high
production rate is required.

Castings basically fall into three categories:
expendable molds/permanent patterns (ex. sand cast)
expendable mold/expendable pattern (wax)
Permanent molds (die cast)

Sand casting is more useful for simple, large parts.  Caterpillar uses sand
casting to produce the heads and blocks (IIRC) for some of their large
diesels.

Lost wax casting can be used to produce some pretty detailed or intricate
castings, which makes it ideal for certain applications.

Die casting is pretty common on non-structural applications... depending on
the quality standards, you can see the ejector marks.  Check out the back
side of plastic furniture on a weapon some time and you should see the
ejector marks and mold lines.  Die casting is cheap once it's set up, so it
sometimes gets a bad name due to the products that people produce with it.

For more information, visit: http://www.engineersedge.com/casting_design.htm

Another method that I don't have proof either way for is powder metallurgy
(P/M), which is widely used in other industries.  P/M consists of "pressing
a powder to the desired shape, followed by heating to an elevated
temperature below it's melting point" (ASM Metals Handbook, 1998).  P/M
allows some combinations of metals that do not alloy well to be successfully
created.  P/M is a growing industry.  Again, I don't have a specific
reference to a firearm application, but I would be surprised if it's not
currently being used by someone.

> What I gathered from "Alloy-Forged" is that a super heated chunk of metal
is
> pressed into a form/cast by hydraulic machinery, to form the shape,
usually
> taking several slamming of the metal into the cast to make the final
shape.  Is
> this correct?

In a rough form, yes.  Forging is important because it reduces porosity and
refines the internal structure, producing a tougher object than a similar
cast part.

Again, I'll reference the engineersedge site as a relatively simple way to
understand the process http://www.engineersedge.com/forgings.htm  If you
want more detail, http://www.forging.org/Design/toc.cfm should provide
enough for the article.

Good luck
-Eric