Go and no-go gauges are .004" apart. This is a pretty wide window. If you are really concerned about where your chamber stands compared to saami, you need to tell your smith. for example, if you have more than one rifles with the same cartridge, it is very convenient to have the headspace within .001" of each other. Then you can set up your sizing die for perfect shoulder bump without having to oversize the long ones. If you want the headspace to match another rifle, take a few pieces of fired brass from that rifle--preferably 1st firing after annealing.
Coincidentally, I just had a guy come by this morning to have his headspace adjusted. He has multiple rifles in the same cartridge and the fired cases from this rifle were .002" longer than the other 2. We took .002" off the shoulder of the barrel to make all 3 rifles headspace the same. He was long in the band, afterwards, he was tight in the band. Go and no-go gauges showed good chamber before and after.
If you aren't shooting factory ammo, then headspace can actually be almost irrelevant since you will set up your die to match the brass after one firing. I do have a friend who is very serious about not overworking his brass. He likes to measure his new brass and make the headspace .002" longer than the new brass so that he doesn't overstretch it on the initial firing. This often results in a chamber slightly shorter than saami.
Bottom line is, go and no-go gauges from different manaufactures should be identical. If they are not, then at least one of them is wrong. I often make my own so I can make the diameter of the base larger and get a better fit in the chamber.
--Jerry