by Ron Spomer
Recently a hunter asked if he should buy a 300 Winchester Magnum or 300 Winchester Short Magnum for his elk, moose, bear, and mule deer rifle.
I told him “Yes.”
“Yes” isn’t a facetious answer because both these cartridges deliver nearly identical performance. Even though the older, longer 300 Win. Mag. holds about 10 percent more powder than the 300 WSM, it drives same-weight bullets only about 50 fps faster than its short cousin. Ballistically it doesn’t really matter which you choose. Functionally, however, it might.
How the 300 WSM keeps pace with the larger capacity 300 Win. Mag. is a bit of a mystery. Powder capacity in the 300 Win. Mag. is around 10 percent greater than the 300 WSM, yet the Win. Mag. does not gain 10 percent more velocity. Part of the reason is the law of diminishing returns. More and more powder behind a same-weight bullet in a given bore size does not increase muzzle velocity consistently The ballistic charts below tell the trajectory story, but here’s the load data used in each of our samples:
300 WSM: 68 grains Norma MRP powder, 190-grain AccuBond Long Range, 3,016 fps MV.
300 Win. Mag: 77 grains Norma MRP, powder, 190-grain AccuBond Long Range, 3,044 fps MV.
300 WSM versus 300 Win. Mag. — Ron Spomer Outdoors is written by Ron Spomer for www.ronspomeroutdoors.com