This phenomenon occurs in all bottleneck cartridges, but it is more pronounced in belted magnums. Many handloaders back the sizing die off one-quarter to one-half turn and lock the ring. This allows the case to headspace on the shoulder. Essentially, the handloader is only neck-sizing the case. Still, the .300 Win. Mag. is a pretty intense cartridge, and all that heat, velocity and downrange energy extract a toll. Even though I adjust my sizing die to headspace on the shoulder, I rarely get more than five reloads before I have to retire a case.

My experience with lighter weight .30-cal. Bullets – 100 to 130 grs. – in this cartridge is limited; however, I have not seen very much accuracy with the ones I have tried. Although the .300 Win. Mag. is often used as a long-range target cartridge, my experience is limited to hunting, so I'll start with the 150- and 165-gr. bullets. Though looked down upon by many today, traditional cup-and-core bullets perform very well within their limitations. The two that I started using many years ago are the Hornady 150-gr. Spire Point and the Sierra 165-gr. soft-point boattail, now called the GameKing.

These bullets can be driven as fast as 3,400 f.p.s., but I get my best accuracy at around 3,200 to 3,250 f.p.s. Eighty-three grs. of MagPro behind the Hornady 150-gr. Spire Point comes out of my 26-inch-barreled Kimber 8400 at 3,240 f.p.s. and can drop five rounds into a 13/4-inch group at 100 yards. At that velocity the bullet breaks up even in a small deer, but everything I've hit with it – from California blacktails to wild pigs – has died very quickly. The Sierra 165-gr. GameKing is another of my favorites. Pushed with 80.0 grs. of MagPro, it leaves the muzzle at 3,140 f.p.s. and five of them can go into 11/4 inches at the 100-yard line. The Swift Scirocco and Scirocco II at 165 grs. show some real potential as well. With 70.0 grs. of Ramshot Hunter, I can get 3,053 f.p.s. and groups right at 1 inches - often with three of the five cloverleafing.

Because of the relatively fast twist of 1:10 inch and the velocities generated by this cartridge, I feel it is at its best with longer bullets. Barnes' 165-gr. MRX bullet in front of 69.5 grs. of IMR 4350 yields a muzzle velocity of 3,071 f.p.s. and groups into slightly less than 11/4 inches. Given the toughness of this bullet I have no qualms taking on elk or moose with it. But the bullet that produced the best accuracy for me in recent tests was the Barnes 180-gr. TSX (Triple-Shock X-Bullet). At 1.389-inches long and with a nearly 3/4-inch long bearing surface, it groups consistently between 7/8 and 11⁄8 inches using either 68.9 grs. of IMR 4350 or 78.0 grs. of Ramshot Magnum. Though it is unlikely I could get the 3,100 f.p.s. claimed by some manufacturers for cup-and-core bullets, I am trying with some powders that may get the bullet to break the 3,000-f.p.s. barrier. I have not yet used this bullet on game, but other TSX bullets in calibers from .270 to .338 have performed perfectly on game for me thus far.

There are heavier .30-cal. Bullets – as much as 250 grs. – but for my uses they cost too much in terms of velocity and trajectory. If I feel the need for a heavier bullet than 180 grs. I'll step up to a .338 caliber.

The .300 Win. Mag. can certainly live up to the all-around cartridge moniker for North American game. Sure, it's a bit much for whitetails, but it surely does the job well. And for large bears, the current thinking is for a larger caliber like .338 or .375, but countless brown and grizzly bears have fallen cleanly to Winchester's big .30 cal. For whitetails in bean fields or across senderos, sagebrush mule deer or even most elk hunting, however, the .300 Win. Mag. is often just the ticket to a filled tag.

Loading the .300 Win. Mag.