You need to hole both lungs. The Moose will then smother in about 30-90 seconds. I use a 358 Norma as my moose gun, unless I shoot the shoulder bone a two lunged moose will generally take the short side of 30-90 seconds to know it's dead...even with 4000 ft pounds on target. My wife uses a 6mm Rem Model 600. With 100 Nosler Partitions or 115 Barnes originals it works pretty well out to about 150 yards taking maybe on the long side of 30-90 seconds to let the life out of a big bull. We are very confident using it within it's limitations.

A 260 would no doubt be a better minimum but the 6 is what we have and it works with some application of discipline. Not sure it's what a beginner should use though.