sentences:  However, the .30-378 Weatherby Magnum is considered the most overbore production sporting cartridge available and is not considered as efficient as the .300 RUM cartridge.In part due to its excessive freebore lengths the claimed velocities by Weatherby is a resultant factor of this freebore length.If chambered to allow bullets to seat to the lands of the rifling the large Weatherby cartridges would exhibit overpressure signs immediately.