I'm thinking of buying one of the hornaday lock and load overall length gauges and a comparator, but theres something im not sure about.

If I have set my rifle to minimum headspace during the barrel install with a go-gauge, will the modified case i use with the OAL gauge get me an accurate measurement? If the modified case is at all larger than minimum wouldnt that be a problem? Maybe theres some way to get a custom modified case?

Im still trying to fully wrap my head around the concept, maybe im missing something.