No, this is not Clark Kent's underwear, it's ammunition. I bought some of those Aguila .22 caliber "Sniper Sub-Sonic" (SSS) rounds a few weeks ago and had a chance to shoot them at my range last weekend. Very impressive stuff.
The case is that of a .22 Short, but the bullet weighs 60 grains, 50% more than the standard .22 LR bullet! Makes for a very funny-looking package, actually. If you didn't know what it was it would make you think someone at the factory in Mexico showed up tanked in tequila and goofed a production run. The bullet is solid, very long (about as long as the case, maybe a bit more) and externally lubricated of course. Aguila says they're suitable for any rifle chambered in .22 LR that's in good condition and that they will work the actin of semi-automatics.
I haven't tried that but I shot some in my old Nylon 11 bolt action, my first .22. I have had this little gun since 1962 and God knows how many thousands of rounds it's fired, but it's still very accurate. I sighted it in with Shorts for squirrel hunting last year and it will shoot the SSS bullet to the same point of aim as the Shorts. At 25 yards off the rest it's no trick to shoot half-inch groups, using open sights, with either type of ammunition. The SSS not only shoots like a Short, it makes no more noise than one, either.
I am told the Israelis have special sniper teams that use this stuff to pick off mob ring-leaders from ranges up to 100 yards away. At that range you would certainly not hear anything at all over the noises of a normal street riot, and of course the bullets don't make the CRACK of a normal supersonic round. According to the news accounts I've read the targets just drop in their tracks, dead from a head shot.
I don't know what I'd hunt with these, being that they have solid bullets; but I suppose they would have quite a bit of penetration. One of these days I'll get my chronograph out and check the velocity, but it's probably in the range of 1000 fps out of a rifle. The most "useful" application I could think of would be deer poaching, as they would be quite a bit more effective on head shots than Shorts, I assume.
You guys who can hunt with silenced rifles (especially at night) might want to give these a try. In a bolt action with a silencer you wouldn't hear anything at all, I'm certain. Jon, just the thing for lamping bunnies.
I think I got them from the Sportsman's Guide, but I'm sure they can be had from other sources.