Gunmetal Paint

Does anyone have any recommendations for a good acrylic "Gunmetal"
color?
Something darker that silver, and hopefully flatter, that could be used
when (wait for it....) painting guns?  Or, say, as a basecoat for
Terminator style robots?

I've got a half-decent Aileen's color called "Pewter", which is much
darker
than any pewter that I've ever seen, but the coverage is pretty bad. 
I'd
like to find a decent paint that I could use extensively, if one should
exist.

John Crimmins
johncrim@voicenet.com