Pictured at left, from left to right: .30-06, .300 Win. Mag., .300 RUM.
Once you understand what a magnum is (see my last blog post), how do you decide if you need it?
Most magnums are bought on emotion. Biggest, baddest, toughest, fastest, hardest hitting. Who doesn’t want to strut around camp carrying a MAGNUM? (Maybe the guys who can shoot?)
Hunting guides regularly report that clients with magnum rifles shoot sub-magnum groups. They’re often incapable of shooting MOM (Minute of Moose). Really. Outfitter Keith Atcheson in Montana keeps a .243 Win. around to loan to his clients after they’ve missed their third or fourth pronghorn.
This doesn’t mean that everyone shoots a magnum poorly, but the increased snort and buck of most magnums does present a learning curve. And if you’re not dedicated to perfecting it, you’re better off leaving the magnum in your dreams.
But what can a magnum do for you? How much and what kind of advantage does it provide over a “regular round?” Short answer: about 30-50 yards more range. Long answer: Keep reading.
Most magnums add between 100-300 fps more velocity to the same bullets their smaller cousins push. That decreases drop, increases energy and decreases wind deflection, as shown in this example. (Note: Each cartridge was zeroed for 250 yards, shooting the same 180-grain spire point, 10 mph right-angle wind).
As the chart shows, differences out to 300 yards are insignificant, except for energy values, and energy doesn’t make that much difference to the game, despite what you hear. A 180-grain bullet through the chest kills about the same whether it penetrates carrying 1,500 or 3,000 foot pounds. No magnum is going to pick an elk or even a deer off its feet and throw it backwards. If you don’t believe it, place a 100-pound bag of sand on a picnic table and try to blow it off with the biggest magnum you care to shoot.
If you’re planning to shoot to 400 yards and beyond, the magnums begin to show advantages. The difference in bullet drop between the .30-06 and .300 RUM at 500 yards is more than a foot. But if you misjudge the range by 100 yards, you’ll miss with either. And if you use a laser rangefinder, you’ll know the exact range and can compensate by using the correct ballistic reticle or dialing your elevation turret.
So what, for heaven’s sake, is the “magnum advantage”? Well, it provides a longer Maximum Point Blank Range—the fastest sighting system a hunter can use to guarantee hits to maximum range without the need to use a rangefinder at all. Check back for full details on that in my next blog post.