Re: Early cartridge rifles

On Sat, 05 Nov 2005 13:38:34 +0000, Dirk Bruere at Neopax
<dirk.bruere@xxxxxxxxx> wrote:

>BTW, why is brass used, and are there any alternatives?

Brass is ductile and cheaper than copper or especially bronze. Copper is
also _too_ soft to make a good cartridge. Even today brass is still
common for cartridges and only aluminium or steel are really
alternatives, both of which require much more careful control of the
drawing process.

All cartridge cases (in fact all small drawn metal articles) are
basically beercans. Owing to the sheer volume and the cost savings
possible from an improved process it's the food industry and
particularly drinks that drive most innovation in thin-wall drawing of
***. Most of these new materials or techniques came about as a better
six-pack - particularly thinwall steel. Brass isn't used for food
packaging because of zinc tainting the contents.

Brass metallurgy is fairly recent though. Although brass and "latten"
are ancient, they were produced by an expensive cementation process from
copper and zinc ore. As zinc vaporises at a low temperature rather than
conveniently melting it's difficult to produce metallic zinc. This kept
the price of brass high until the mid-18th century when smelting of zinc
metal was developed and brass became cheaper.

In the period up to the mid-19th century brassmaking developed further,
particularly cheap machine rolled ***. Before this, latten (brass
***, widely used for pots and pans) had been made slowly and
expensively made by water-hammering a brass ingot into a thick ***.
New alloys allowed machine rolling far more quickly, and into thinner
sheets. The rolled brass cartridge with a spearate base was now
practical to manufacture, although still a problem in service with the
base separating.

Cold-drawable brasses, and the one-piece cartridge case needed further
developments of brass alloys and the 70/30 (Cu/Zn) cartridge brass
alloy, rather than the common "yellow brass" 67/33 alloys or the Muntz
metal 60/40 alloys. These simple proportions aren't the real story -
drawable brass depends more on the absence of impurities than on simply
varying the Cu/Zn ratio - and that relied on further developments in the
zinc smelting processes to produce purer zinc. This was the real limit
on the availability of a cold-drawing brass.

As to the problem of cartridge cases separating, then this was largely
encountered with the Martini-Henry and it's bottle-shaped cartridge.
This used the base of the .577 Snider cartridge, necked down to the .450
Martini-Henry bullet. The crimp was often uneven around the neck and it
was fire-forming of this crimp tightly into the chamber that began the
split, not just the extraction force. Cylindrical cases in rolled brass
had much less trouble.

.