The .270 Weatherby Magnum was the first belted magnum based on the .300 H&H Magnum to be developed by Roy Weatherby. It has the characteristic double-radius shoulders and is necked down to accommodate the .277in bullets. Being a proprietary cartridge, the .270 Weatherby has no official SAAMI maximum pressure limit. Weatherby factory ammunition is loaded to 71,000 PSI. The first Weatherby cartridge to be used in Africa was the .270 Weatherby on a jackal on June 8, 1948.