The bolt head is too large to pass through the receiver. How does the bolt head come off? Not sure of the caliber. It is one of the Navy rifles with the anchor and serial number and inspector's innitials on the receiver ring.IIRC, you rotate the extractor out of the way, open the bolt, squeeze the trigger and pull the bolt to the rear and out. Since the extractor is missing on yours, you should be able to skip that step.
Mine is in the safe downstairs. I can check later tonight.
What caliber? Mine is .30-40 Krag.