It is a beltless, rebated rim cartridge based on the .300 Remington Ultra Magnum case shortened .090" loaded with a .338 caliber bullet. The .338 Remington Ultra Magnum ranks third after the .338 Lapua Magnum and .338-378 Weatherby Magnum in cartridge-case capacity. Because this cartridge already operates at very high pressures (65,000 PSI), Handloaders cannot give significant improvements over factory ammunition as many handloaders have done over the years with more conventional, lower pressure rounds.