Winchester Super Short Magnum.
NOTE: Although we are currently not manufacturing any rfiles in WSSM calibers, many past Browning rifles were. For those who have an existing WSSM-chamberd Browning rifle, this information below can be interesting.
If a bullet traveling at 4,100 feet-per-second sounds appealing to you, then prepare to feel great. This performance has been achieved and is available to satisfy the ever-changing needs of hunters and shooters.
In 2003, with inspiration from high-velocity benchrest cartridges like the 6mm BR and 22 PPC, the 223 and 243 Winchester Super Short Magnums (WSSM) were introduced. Once again, the way we hunted, shot and perceived magnum calibers changed. These calibers took the groundbreaking short magnum concept — which originated with the 300 Winchester Short Magnum — one step further, becoming the hottest, highest velocity production cartridges available.
The impressive speeds of the WSSM are achieved by putting a lightweight bullet on top of a short, fat, high-volume case. This basic concept resulted in muzzle velocities of 4,100 fps with the 243 and up to 3,850 fps with the 223.
The short, fat shape of the WSSM cartridges produce a more uniform powder burn, providing consistent shot to shot velocity and better accuracy.
Also, because the burn is so efficient, a shorter, stiffer 22" barrel is used to further reduce weight and improve accuracy.
To ensure reliability, the WSSM cartridges, with their short 2.36" overall length, necessitate a shorter action. Because of this, a super-short action size was designed for the A-Bolt rifle. The super-short action is not only shorter; it’s stiffer, quicker and lighter. Meaning WSSM rifles shoot straighter, faster, come to the shoulder quicker and are easier to carry. With that in mind, the A-Bolt WSSM with its super-short action may become your favorite benchrest rifle, favorite varmint rifle and favorite mountain rifle all rolled into one.
Although not as commonly found as in the years when they were originally announced, the performance speaks for itself.
A few interesting links.
243 WSSM Wikipedia aritcle.
223 WSSM Wikipedia article.
25 WSSM Wikipedia article.