If the headspace is too long. If too short it won’t chamber or when fired won’t extract. Headspace is not the length from base of cartridge to bolt face. It’s from chamber to bolt face. You adjust headspace at the barrel/receiver. The bolt itself has no adjustment.
That is correct for cartridges that headspace on the shoulder of the cartridge. Some magnum cartridges have a belt in front of the rim and the round headspaces on the belt. Rimed cartridges like the 30-30 headspace on the rim.
Primary headspacing is usually set as you describe - where the barrel and receiver join (at least for most 20th-century military rifles). There are oddballs, though - in tilting-bolt designs like the SKS and the FN-FAL, headspace is tweaked by adjusting the thickness of the bolt locking shoulder. The HK G3 (HK-91) and its small-bore relatives rely more on bolt-to-bolt carrier gap than headspace, due to the roller-locking design being adjustable with different diameter rollers.