The 7mm STW uses a parent case of the 8mm Remington Magnum, which, of course, is necked down to 7mm and its case taper straightened slightly. The new round has become very popular among long-range deer hunters.
“We kept watching the sales of 8mm Remington Magnum brass climb up and up,” said a Remington ammo-development specialist. “We knew from gun sales that that it wasn’t being used in rifles chambered for that caliber. and it became apparent that the popularity of the 7mm STW was just too big to ignore any longer.” Once these trends were clear, Remington legitimized the popular then-wildcat round.
Initial factory loads feature a 140-grain bullet with an advertised muzzle velocity of 3,325 fps. I found that my rifle’s 25.5-inch barrel actually exceeded that, averaging 3,359 fps. Handloads should be able to boost this velocity by a considerable margin. Some reports have 140-grain bullets running over 3,500 fpsWe withhold judgment about whether those speeds are achievable with mainstream loads.
Based on our experience with the round, we think that the 160-grain bullet will be more practical for this cartridge. Indeed, the Barnes #1 Reloading Manual shows several loads that exceed 3,300 fps using this bullet. Also, Remington will likely bring out more factory loads soon. With the current factory loads, the 7mm Westerner has an 11-percent energy gain over the 7mm Remington Magnum and a 7.1-percent gain over the 7mm Weatherby Magnum at 400 yards.