I have a Hornady overall length gauge. I use it for my 308 and have a threaded dummy case. I'm about to start loading for a 20 Tac which uses the 223 case necked down. The diameter of the head of a 223 case looks very similar to that of the thread body on the gauge and I doubt it will be possible to drill it out and thread it..
Do Hornady supply a different gauge for the smaller calibres or is there an adapter available?