take a live round and find some thin scotch tape, thinner the better.
apply one layer of scotch tape to the case head, trim off excess from the edges and do headspace check as if round was a headspace gauge. it will close on one layer of tape. add another layer and repeat. if it still closes add another layer. and so on and so forth until it doesn't close anymore. count layers as you add them. after you built up enough layers that bolt no longer closes you can multiply number of layers by thickness of the tape and you will know how far off is your gun.
different gauges from different manufacturers will have different tolerances. some are tighter than others. another way you can do this is to fire a round and then use hornady headspace comparator on fired case vs unfired to measure the difference. you can then judge if if brass growth is within spec or not. it'll stretch a little and it'll be evident if brass stretching excessively.
i'm 100% positive your rifle is fine. your gages probably just more conservative than the ones bulgarians used.