.300 KONG

WILDCAT CARTRIDGES

- Layne Simpson

I had the great pleasure of knowing Roy Weatherby. Back then people took pen and paper in hand and wrote letters, and I have saved all received from Roy on various subjects. Several were on an old wildcat he had formed by necking down the .378 Weatherby Magnum case for .308-inch bullets. His reason for doing so was as interesting as the cartridge.

During the late 1950s, Uncle Sam contracted Weatherby to deliver a rifle capable of producing uncommonly high velocities. It would be used for testing the penetration resistance of various types of experimental materials when impacted by high-speed projectiles. So Roy necked down his .378 Magnum case to .30 caliber and seated a saboted .224, 30-grain solid copper bullet made by Vernon Speer, atop a hefty charge of military surplus powder sent to him by Bruce Hodgdon.

Not quite satisfied with a velocity of 5,000 fps, he then tried an experimental powder from Hodgdon and peaked at 6,000 fps. If not for its eventual popularity among members of The Original Pennsylvania 1000-Yard Benchrest Club, the .30-378 Magnum story would likely have ended there.

Like all Weatherby cartridges, it has a double-radius shoulder. Roy once told me he went with that shape for one simple reason – to make it difficult for gunsmiths across the country to grind chamber reamers. I could never talk him into offering his Mark V rifle in .30-378 Magnum, but not long after his son Ed became president of the company, the idea became somewhat easier to sell. Possibly to get me off his back, in 1990 Ed sent a Mark V action along with a note requesting that a custom rifle be built around it. I immediately forwarded the action on to Kenny Jarrett and later informed Ed of the accuracy and velocity we were getting.