A friend now owns two of these. He asked me if one could be opened and rebored to 450 Rigby or 450 Dakota?

Do these rifles have hammer forged barrels? If so, how would one likely respond to the stress relief of being cut rifled to a larger bore size? The default answer is "buy a cut rifled barrel to the same outside dimensions, then transfer sling swivel and front sight band over to new barrel.

Any informed views would be appreciated.

L/D