Will- If the .458 round you're discussing is the one I'm thinking of, it's been around since 1962. Frank Barnes invented it to duplicate 45/70 ballistics in a short action (722)test rifle. The logic was it could be used in other rifles to accomplish whatever the goal was. Didn't shoot a whole lot of cinder blocks in Viet Nam. At any rate, it became the .458x2" or the .458 American. Seems like I saw one for sale in Alaska. Cheap.