If you think the 300 Win. Mag. is a significant improvement over the .30-06, wait until you shoot the new ground-breaking rimfire cartridge from Winchester. I'm not allowed to disclose its name or caliber yet, but it's scheduled to storm the market in 2013, beginning as soon as early or mid-March. Its performance exceeds current cartridges in its class by a wider margin than the 300 Win. Mag. over the .30-06.
I don't say this based merely on rumor or manufacturer hype. I've shot the new round. It does everything Winchester says it will. The bullets fly from the muzzle 500 fps faster than any other rimfire cartridge I'm aware of. At 250 yards, they retain nearly double the energy of the next-best round in their class. During my testing off sand bags from a portable bench, five bullets clustered just over 1 inch at 100 yards in light but variable winds. A single four-shot group went into a .39-inch spread, and one 300-yard four-shot group fell inside of 2.5 inches. All this was accomplished with a prototype bolt-action rifle so unrefined that cartridges had to be hand fed and extracted from the chamber with a knife blade.
Ballistic coefficient and velocity of the bullets are so high that this new round should hold a Maximum Point Blank Range of 250 yards on an 8-inch target. This means you aim at the center of the 8-inch target and hit it at any and all distances out to 250 yards. Last but not least, the new rounds should cost within 10 percent of currently available rimfire rounds in their class, or about a third less than some centerfire rounds with similar ballistic performance.
Because dimensions of the round are significantly different from any others currently made, at least one gun maker is reportedly building newly designed bolt-action rifles to fire it. Two more are reportedly working on additional models. Whether those are bolt actions, break actions, levers, semiautos or something else remains to be revealed.
“New” cartridges are a tried and sometimes true method for ramping up sales in the shooting industry, but most of them provide only incremental improvements over existing rounds. This new cartridge from Winchester is more than that. Much more. It should be a game changer.