The O'Connor .416 is cataloged in Robert Anderson's book Jack O'Connor.

Enfield action, 24-inch Apex barrel, Biesen stocked, Weaver K2.5 in a G&H side mount. Weighed 10.5 pounds. Factory ammo was not readily available, so Jack made brass by turning the belts off .378 Weatherby cases and running them through the full-length sizing die.

Photo of it in the 2nd & 3rd editions of Jack's The Rifle Book.