There is more to properly setting your size die for a particular rifle than just dropping the case into a go/no go gauge, but unless you just have to have the 'inth degree of accuracy, I wouldn't bother. A rack grade Garand is not one that would benefit from it, either, I'd just FL size my brass and go with it... because that's what I do.
I agree with that. Everyone should take those esoteric bench rest techniques and throw them as far out as you can, in front of the firing line when loading for semi auto's. You want plenty of clearance between the case and chamber, and techniques like neck sizing or partial neck sizing will, in time, result in an out of battery incident if you use Federal match primers in your Garand or M1a. First and foremost you want safe ammunition that will feed and extract each and every time.
You cannot measure chamber headspace with a cartridge headspace gauge and fired case because in a semi auto the case is stretched on extraction. You can in a bolt rifle. If you want to determine the exact chamber headspace of your rifle you will have to do with with chamber headspace gauges. And that is not necessary, as long as the rifle accepts the Go and rejects NO GO it is safe. Cartridge head space is best measured by cartridge headspace gauges, and to reduce the base to shoulder distance, you screw down the die. But, I have several Lee sizing dies that were so long that even when they touched the shell holder, I could not size a case to cartridge headspace gauge minimum. What I had to do is grind material from the bottom of the sizing die. I then sized a case, used a case gauge to measure the base to shoulder distance, and keep grinding and sizing until I had a sizing die that sized a case to gauge minimum.
