Mike Bailey:
Missed your earlier post, sorry. PM sent, but decided to respond anyway.
Not a croc-shooter myself, but own 2 skulls under permit and there are many more available for casual study in the Northern Territory. I believe the CNS brain/cranium/atlas of a large croc to be more like cigarette-packet size. The shot will invariably be made from a very steady rested ambush position. A good DR (..and a good DR shooter!) should be able to manage this out to 100 yds, but closer is better of course!

If a second rifle is taken, then an accurate scoped medium-bore bolt-gun is a better option for croc without doubt.

But speaking personally, I wouldn't 'handicap' myself on buff etc with a medium-bore bolt-gun just because a croc was on licence!