Whenever the bolt moves foreward of a cocked hammer it is possible to pull the trigger and the hammer will drop.
The carbine firing pin has a tang at the rear that must align with a slot in the receiver in order for it to move foreward and hit the primer.
When the firing pin tang is aligned with the receiver slot the bolt should be fully locked and safe to fire.
The early carbines had a type 1 firing pin. It was found that this pin would sometimes allow the pin to hit the primer with a partially locked bolt , that is , only the right lug engaged.
This would result in a broken bolt and a damaged receiver.
Case length is very important with the carbine and when reloading , cases must be inspected and trimmed as needed to prevent firing from a partially locked bolt.
If your carbine has a type 1 firing pin you might want to replace with a type 2 or 3.
Jim C