Gentlemen:
Here is the first story about "that" shotgun conversion I tossed up on the web some years ago:
"Dancing with the Fat Lady"

...and the story of its last hunt in my hands before moving it on to Mick (.264):
"Last Dance with the Fat Lady"

I do miss that interesting rifle, but have since transferred my affections to an Army & Navy .577 x 2 3/4 on a Webley screw-grip (A&WC) action.

Also I am reminded that the Browning BSS action was considered suitable for conversion to some NE chamberings by a number of reputable gunsmiths in the past.

Hope this is of some use.