9ThreeXFifty7

Years ago in the American Rifleman there was printed a sequence of photographs showing your fellow Idahoan, Elmer Keith, shooting a Mauser single shot anti-tank rifle which had been rebarrelled to .50 BMG. Elmer was shooting off sandbags placed on the roof of a car, I believe, and the second photograph showed the rifle in full recoil and Elmer's signature ten gallon hat flying through the air. The next month someone wrote in and remarked that he was glad that Elmer had finally found a cartridge powerful enough to dispatch a sick jack rabbit.

I once toyed with the idea of building a rifle using the .50 caliber cartridge developed as a spotting round in conjunction with the 106mm recoilless rifle. This was a normal .50 caliber BMG case reduced in length and capacity to produce a muzzle velocity and trajectory identical with that of the 106mm projectile. The idea was to fire tracers at the target using the .50 caliber spotting rifle, which was parallel mounted on the side of the 106mm tube, and as soon as the tracer hit the target, to fire the 106mm round, which would strike at the same spot. The same knob traversed the weapon and fired both the spotting round and the main tube.

I decided, however, that if I was going to shoot a 750 grain bullet, I would prefer it to be a larger diameter than .50 caliber, and that was the genesis of my rimless .577 round.