Mr. max:
It certainly would be a treat to examine the rifle! I have been wanting to closely examine a Selous plated Gibbs for a good while with an eye to duplicating the plates. Mr. Mann objects because they cover up his pretty wood, but I really want to do this.
There was a .465 express chambering but, even though action 710 was a late action, I don't think the chambering existed when the rifle was build. Howsomever, it is entirely possible that the action was rebarreled at a later time.
A chamber cast and bore measurements are in order. So are PICTURES!
Respectfully,
Glenn