Bolt head question

[hawk-i]

why is the rifle s/n matched to the bolt head (last four digits stamped on head) and what implications does this have when swapping out a bolt head in a calibre change.
Model 12 VLP, 22-250

[Eric in NC]

Means it was headspaced to that rifle/barrel/receiver combo at the factory.

Implication for swaping out bolt heads or barrels is that you have to re-set headspace.

[hawk-i]

Thanks Eric,
Your reply sounds reasonable....mystery solved!!!