Thanks gentlemen. I had considered going with a Krieger barrel for the .465 NE, with specs of .459/.468 and 1:18 twist, based on reports that Ross Seyfried wrote up an original Gibbs in the chambering with a groove diameter of .470 or larger in the Summer 2004 Double Gun Journal. I just ordered that back issue.
Bob, I am absolutely certain the longer No. 2 case will fit easily "round the bend" in a Martini. based on the Greener I once owned chambered in .577 3-inch BPE. This large, straight case, loaded with a 650-grain Woodleigh to the cannelure, fit the Greener just fine.