Commercially bolts would be lap to fit the contact points on the receiver. Headspacing would be achieved by reaming the chamber to the proper depth. In the military (US) the armorer would fit a bolt from a pile that were on hand until one properly fitted. Grinding is big no-no since the grinding could go below the heating of the lugs on the bolt and be extremely dangerous. Given the numerous versions of the Garandicon that the Italians fielded it possible several parts from other versions were mixed in with the parts kits and replacement parts. Parts are parts. Sadly full guns could be imported back into the US. We have seen parts kits without the receivers and barrels.

--fjruple