I get it, but I have never had a head space issue with mosins that were surplus C&R imports, where numbers matched (or were made to match / strikethrough, etc.) when rearsenaled. I've used the empty case with masking tape spacers, and the tire/duct tape/string method, but I'm at the point where I'll just do a empty case inspection for ominous indicators. Never get any. Not saying it's not the right thing to do, however, I don't recommend folks go getting head space gauges for everything they collect either. That's just me.
Liberty and freedom often offends those who understand neither.