As noted, headspace refers to a dimension in the rifle.
However, if you are talking about checking the cartridge's "headspace clearance" (various terms are used for this, including "cartridge headspace" and sometimes simply "headspace"), then that involves a different measurement.
Chamber headspace gauges can't be used to measure cartridge headspace.
The simplest tool is something like a Wilson type gauge -
http://ads.midwayusa.com/product/550...358-winchester
Note that the description refers to the dimension as "cone to head".
As jepp2 noted, you need to set up your resizing die correctly, or you can create a condition known as "induced excess headspace". This has the same consequences as a rifle with a chamber with excess headspace...case head separation. (Which can be very hazardous to the rifle and you.)