From Layne Simpson:
My first store-bought deer rifle was a Marlin 336 in .35 Remington, and I liked the caliber so much that I eventually got around to hunting with rifles in .358 Winchester, .35 Whelen and .358 Norma Magnum. After using a rifle chambered for the latter cartridge on a moose hunt in Sweden, I decided to neck up the 8mm Remington case to .358 caliber and call it the .358 Shooting Times Alaskan. Kenny Jarrett built the first rifle in that chambering for Bob Nosler and I got the second one, a switch-barrel Model 700 with its other barrel in 7mm STW. A few months later I headed to Alaska, where I bumped off a brown bear with the 250-grain Nosler Partition loaded to 3,000 fps.
I introduced the .358 STA to the world in 1992. Unlike the .257 STW and 6.5 STW, which are nothing more than the 7mm STW case necked down with the original body taper and shoulder angle retained, the .358 STA is the 8mm Remington Magnum case necked up and fire-formed to minimum body taper and a 35-degree shoulder angle. Cases can also be formed by necking down and fire-forming the .416 Remington Magnum case. When both are loaded to maximum chamber pressure with 250-grain bullets, the .358 STA is about 200 fps faster than the .358 Norma Magnum. It pretty much duplicates the performance of the 1920s-vintage .350 Griffin & Howe Magnum and the .350 Super Magnum, which was introduced by Art Mashburn during the 1940s. All are on the full-length Holland & Holland belted case.
At that point I had no intention of adding additional members to this particular wildcat family, but letters from readers who requested cartridges of other calibers eventually caused me to introduce the .257 STW in 1998. Lex Webernick built the rifle, and I first used it and a handload with the Nosler 100-grain Ballistic Tip at 3,700 fps to take a nice Coues deer down in Old Mexico.
About a year later I came up with the 6.5 STW, not because it had received a great number of votes from readers but because I was quite interested in that particular bullet diameter. The first rifle in that chambering was
built by the Canadian firm Prairie Gun Works, and the first game I took with it was a black bear on Vancouver Island. The handload I used pushed along the Nosler 140-grain Partition at close to 3,200 fps.
When both are loaded to the same chamber pressures and fired in barrels of the same length, I find the .257 STW to be about 200 fps faster with all bullet weights than the .257 Weatherby Magnum. I also find the 6.5 STW to be about 200 fps faster than the .264 Winchester Magnum. Whether that much gain in bullet speed is worth the effort is for the fellow who will be spending his own money for a new rifle to decide.
There's a good pic here of the cartridges:
http://www.rifleshootermag.com/ammunition/7mmstw_071207/index.html