9mm bullets. 
I plucked these off some 9mm rounds I got in California many years ago.  But you can pretend they were used in a bank robbery or something, it that makes them seem more interesting.  The copper color comes from a thin plating of copper, but inside it's all hot lead. 
The sound for this sample is a nice shot borrowed from da-admiral.com. 
Source: Gun Shop in California 
Contributor: Theodore Gray 
Acquired: 15 April, 2002 
Text Updated: 11 August, 2007 
Price: $0.20/bullet 
Size: 0.5" 
Purity: >95%
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