The words "brass" and "bronze" are ancient terms. Then simple (and misleading) definition is that brass is an alloy of copper with zinc. Modern cartridge brass is a NOMINAL 70% copper, 30% zinc. Bronze used to be an alloy of copper with tin. Civil War bronze "Napoleans" were, I believe, 90% copper and 10% tin.
In our day we still use the terms "brass" and "bronze" but in fact there are around 500 different standard copper alloys called by these names. About all they have in common is some large amount of copper.
Here are portions of something I wrote titled Gunmetals Never got around to publishing it, just use it as a reference for myself.
The first copper alloy in history was arsenic bronze, followed by tin bronze about 5000 B.C. in the far East. The weapons Homer speaks of in the Iliad were all of tin bronze . . . The SAE in 2004 listed over 500 different alloys, whose names include various combinations of the words copper, brass and bronze. The alloying elements used now cover the alphabet from the most ancient, Arsenic, to the newest, Zirconium.
. . . remember the differences amongst tin bronze and brass, copper and gilding metal. They are all different shades of red and yellow. Nickel silver is nearly white. This name is often confused with a similar alloy called German silver, which has a slight yellowish cast to it. Bells are made of bronze with about 22% tin and 78% copper. This makes a fairly hard alloy with a good ring. This hard metal may also crack if the bell is hung wrong. If one is to melt down church bells to cast cannon, one must add some copper to the melt so the metal is ductile enough for a gun.
Many alloys, called variously brass or bronze, are alloys of copper with both tin and lead. One such is cast Gunmetal, also known as Government Bronze G, with the Unified Numbering System identification C90500. The alloy is nominally 88% copper, 2% zinc and 10% tin. In practice a little lead may be added to improve the soundness of the casting, and for machinability
. . . store neither your modern ammunition, nor your powder flasks, either in the barn, or near the kitty litter!
The cracks in the (bronze revolver, long stored in a Tennessee horse barn) frame, shown here, along with several others in the grip frame, bring up an important point about copper alloys. They are all subject to “season cracking” in the presence of ammonia or other nitrogen compounds. A 1942 metallurgy book states: It is well known that the atmosphere in the vicinity of stables and farm yards is a very dangerous one for stressed brass, and in olden times a car garaged in farm buildings often exhibited many season-cracked brass parts. It is not such common knowledge that the urine of rodents and of some other animals—for example, cats—quickly produces season-cracking, and that many tons of cold-drawn brass have been ruined annually owing to the unwelcome attention of mice and rats in old warehouses. . .”
Brass is normally thought of as copper with zinc added. Modern cartridge brass is 70% copper 30% zinc. Copper-zinc alloys range from 5 to 40% zinc.
Early metallic cartridges were of what today is called “gilding metal”, an alloy of copper with just 5% zinc. The zinc improved both strength and ductility, so the metal better withstood drawing into a cartridge case.
Below is a .45-70 “Multi-Ball” cartridge, designed to more effectively destroy the last free people in North America. The case is 94.8% copper 5.2% zinc, known at that time as Bloomfield’s Gilding Metal.
This 5% zinc alloy (almost as red as copper) is stronger than pure copper, but not as strong as the 70% copper 30% zinc cartridge brass used today. Gilding metal is now used for bullet jackets (metal patched bullets, to use an older terminology)
Lead in these and other brass parts is the reason one must not heat brass to bend it. The lead melts, or comes close to melting, and with a little bending it runs along the grain boundaries so that the part breaks, or crumbles, in two. Bend all brass, new or old, at room temperature
