Okay, so I was GIVEN all this reloading stuff and am a beginer reloader. I've done a few thousand pistol cartridges and am now trying a rifle (bottleneck) cartridge for the first time. I bought the Dillon .223 3-die set (because of the carbide expander feature) and am trying to set up the sizing die. The Dillon literature "strongly" suggests using a headspace gauge to set up the resizing die. Among the equipment I was given, I found a brand new complete Hornady headspace gauge kit. The instructions are very limited and not much use (did get some info on Youtube). All right, now I am guessing I can determine the length from the bottom of the case to the "datum" line (yes, I used the correct bushing). As is shown in the pic, that measurement is 1.467. My question (perhaps stupid) is how can this be applied and used to set up my resizing die? Is there some specific measurement I should be trying for? Again, I am new at this.....any explanation or answers are appreciated.