Winchester has been tooling away on an all new rimfire cartridge, one that might see a bit of success compared to other recent and even less recent rimfires: the .17 Winchester Super Magnum. Early reports of its performance alone should be enough to grab the attention of rimfire fans.

That’s because this isn’t some hopped-up, over-pressure .22 caliber case that’s been necked down to .17 cal. For this new cartridge, Winchester tapped a different market entirely.

“This is not jut a hotter loaded .17 HMR,” said Brad Criner, senior rimfire product manager at Winchester, to Mike Schoby at Petersen’s Hunting. “We have a power fastener division of the company… you know, they make cartridges for power nail guns and such. Well, we based this case off of the .27-caliber power fastener case. It gives us more case capacity, can handle higher pressures and ultimately more velocity. Lots more velocity.”

With the larger case capacity, .17 Winchester Super Magnum easily outperforms other rimfire cartridges, including .17 Hornady Magnum Rimfire and .22 Winchester Magnum Rimfire, by about 30 percent in terms of foot-pounds. Depending on the load, .17 WSM is capable of generating about 400 foot-pounds of force, and can have a muzzle velocity of up to 3,000 feet per second.

Those types of velocities combined with 20- and 25-grain bullets will make the .17 an instant hit with varminters and competition shooters. Big .17-caliber bullets have great ballistics for rimfire cartridges, and the high velocities will mean even flatter trajectories and a greater effective range.

“The new load from Winchester spits out the 20-grainer at 3,000 fps and a 25-grain load at 2,600 fps with energy levels right at 400 ft. lbs. and 375 ft. lbs. respectively—150 pounds more than the 17 HMR and solid 60 foot pounds more than the hottest .22 Winchester Magnum loading!”

“When it comes to critical factors like wind drift and drop, the Winchester Super Magnum beats the HMR by half, and when it comes to the wind-challenged .22 Win. Mag., it simply leaves it in the dust.”

Naturally, as a new rimfire cartridge it’s got some seriously entrenched competition. .22 Long Rifle isn’t going anywhere anytime soon, but this will put a lot of pressure on .22 WMR and .17 HMR, particularly for rifles and activities based around them.

The other thing is always price. If .17 WSM costs as much to shoot as .223 Remington, then people are going to have a hard time not reaching for centerfire alternatives. We hope that the mass production of industrial .27-caliber cases is enough to keep prices down; if .17 WSM is priced in line with .22 WMR and .17 HMR, well, those rimfires might not be long for this world.

Of course, there are other obstacles. Winchester can’t be the only company making .17 WSM rifles for it to be a real success, and the more companies making .17 WSM ammo the better. And as always, we like our ammo to have SAAMI specifications. Wink, nudge.

This new rimfire cartridge is a different animal entirely. We can’t wait to see the new crop of rifles Winchester has for this cartridge and we hope to see other companies get on board if this cartridge lives up to some of these early expectations.

And we really like that Winchester is doing something completely different without also reinventing the wheel. .17 WSM is going to be a hot topic this year, one we plan on covering thoroughly.