Ross MkIII / M10 Bolt Issue

[Bluenoser]

The rivet, which is clearly visible when present, does not prevent disassembly, but it does somewhat complicate both disassembly and reassembly. I see no rivet on this bolt.
It has been a while since I last disassembled a Mk III bolt but, as I recall, the bolt head does not come out in one simple continuous rotation. I seem to remember it rotating out part way and then rotating slightly before rotating out the rest of the way. I always find it to be a bit of a fiddly process.