Here's an original Striker 12 for sale at AA right here. This one's been there forever.
Striker 12 $1,550.
Here's what I know about them:
The original Striker 12 revolving cylinder shotgun (made by Reutech Defense Industries of South Africa) has a 12 round cylinder with 12 gauge, 2.75" chambers. The mechanism is DAO and each pull of the trigger allows the cylinder to advance to the next chamber before firing. Due to the size of the cylinder, using a pawl & ratchet type system like on a normal revolver is impractical, so it's driven around by a pre-wound clockwork spring. The spring is wound up before shooting by use of the winding key on the front of the cylinder housing, below the barrel. Reloading is accomplished through a single-action style feed gate behind the 1 o'clock chamber (as seen from behind) and a spring-loaded ejection rod runing along the right side of the barrel. Durring reloading, a lever on the top of the cylinder housing is used to allow the cylinder to advance without firing the gun (I think.)
While it does give you twelve shots, it takes forever to reload. Open the loading gate, eject each fired shell and replace with a fresh one, then hit the advance lever and repeat for each chamber. After reloading all twelve chambers, close the loading gate and rewind the cylinder spring. Not exactly combat expedient.
One other problem I've heard of it having is a flaw in the trigger mechanism, where not pulling the trigger fully to the rear before releasing causes it to skip multiple chambers without firing.
The Street-Sweeper is an American made clone of the Striker 12.
The protecta (also made by RDI) isn't quite the same thing. The cylinder on the Protecta is manually rotated by twisting the foregrip counterclockwise then clockwise (as from behind) on the axis of the barrel. While this does get rid of the chamber-skipping problem, it reduces your rate of fire (if you really care) and reduces your capacity. While it uses almost the same cylinder as the Striker, the loading gate has been removed and a sideways ram attached to the right side of the reciever sits behind the 1 o'clock chamber position. The ejection rod has been modified into a gas piston which automatically ejects the 1 o'clock shell when the gun is fired. This means you can't use 12 shots in it, since the last round in the sequence is ejected by the first shot. The last (eleventh) shot is also not ejected, because there's no other shell to fire to eject it.
Most all Striker, Street-Sweeper, and Protecta shotguns are equiped with a fold-over-top stock, perferated metal barrel jacket, and front grip. They are also often equiped with flash-hiders (I think that's what they are, they might be muzzle breaks of some sort,) like the one in the AA auction above. As far as I know, the Striker 12 and Street Sweeper have both been out of manufacture for quite some time now, however the Protecta may still be in production. That doesn't really matter here, since the've all been classified as DD's by the mighty BATF. That also makes them (un)fairly expensive.
The final verdict: cool toy, impractical combat weapon. If using one in a fire fight, fire twelve shots, drop it, pull out your backup weapon, and make reloading it a New Year's resolution. You
do have a backup weapon, right?