The .30-378 case holds as much as of powder without requiring a compressed load. This allows the cartridge to develop more energy than the .300 Remington Ultra Magnum and .300 Winchester Magnum, especially when handloads are used. Note: Using the bullet weight and muzzle velocity in each cartridge that provided the maximum muzzle energy. Data for the .30-378 is from. Loading data for all other cartridges can be found at