I never heard of chrome-silicon steel, but ran across an article in
Defense Tech Briefs (page 10 of the April 2013 issue) talking about the
use of this steel in places where there wasn't enough space for a
spring made of carbon steel.

Nor had I ever heard of springs made of stranded wire.

http://www.defensetechbriefs.com/component/content/article/16197

Here is the same article without so many ads:

http://www.ctspring.com/press/2012/03/stranded-and-shaped-wire-springs

And not just for recoil:

http://www.ctspring.com/products/springs/magazine


Joe Gwinn - Apologizing for the on-topic content.