I have checked the headspace and it is barely acceptable.
What's "barely acceptable"?
I'm trying to figure out what all this extraneous discussion is about.
Did it pass a field gauge test, or not?
If the rifle has excessive headspace- usually worn bolt lugs/receiver- don't shoot it. It's mechanical wear of the lugs and mating surfaces on the receiver that increase headspace over time- not throat erosion/chamber dimensions.
You can try swapping bolts to decrease the distance from the boltface to the cartridge datum line.