The .357 Magnum was a performance breakthrough when introduced in 1935. The new handgun cartridge featured a 158 grain bullet at speeds over 1500 fps. These numbers seem mundane now, but were a significant departure over the general use .38 Special in the 30’s.

Smith and Wesson brought the large frame Registered Magnum revolver to market along with the .357, but the depression and WWII delayed the introduction of other revolvers robust enough to shoot the new ammo. In the meantime, the cartridge was detuned. Ammunition makers offered the .357 Magnum, but at a retail loading short of its maximum potential.

Production of the Great Western Frontier model included rigorous heat treatment of centerfire cylinders (Edwards, and the Encyclopedia of pistols 1961). Great Western’s testing demonstrated that Frontier models would withstand loadings a bit in excess of Smith and Wesson’s original specifications. With a revolver that could shoot the .357 at 1600 fps, for a brief period over 1954-55 Great Western could claim to have the most powerful handgun in the world. They called this hot load shooting revolver an “ATOMIC”, though there may not actually be any case differences from regular .357 Magnum ammo.

With Smith and Wesson’s introduction of the .44 Magnum it became a moot point. The .357 Atomic was no longer the world’s most powerful handgun cartridge. Great Western sold quite a few Atomics, but did change over to a conventional .357 Magnum rollmark in 1958, at about serial GW19400

Frontiers in .357 Atomic are neither plentiful nor unobtainable. Production likely numbers somewhat below .45 Colt or .38 Special models.

After Great Western’s closing, Herters and Hawes went on to chamber their JP Sauer made SAA clones in .357 Atomic. Herters may have offered headstamped brass at the time, but cartridge cases like these have not seen by the author or other advanced collectors.

Rollmarks:

.357 ATOMIC, when encountered serials GW1 – GW19400.

.357 MAGNUM, when encountered GW19400 and after.

Models / barrels: All models were made in .357 except the Sheriff. No Sheriff’s have been observed in .357. It’s unlikely but not out of the question that a Sheriff in .357 will be encountered.

Build / Construction: It’s said in places that the Atomic was to have a cartridge 1/8 inch longer than the Magnum. This we are yet to know, as brass for the Atomic has never been encountered. Great Western’s Atomic cylinders are fractionally longer than the 1.60 that is standard for a centerfire cylinder of Colt dimensions. This lends credence to the idea that the Atomic cartridge was to be longer. Chamber castings from these cylinders also show room for the longer cartridge (this observation courtesy Carlyle Pack)