Abstract: A target practice system including reusable cartridges for firearms and a bullet trap for stopping the flight of projectiles from the cartridges. The case of the cartridge is adapted to receive the projectile, or alternative standard cases may be used. The projectile has a cylindrical core of a diameter less than the rifling of the firearm and axially spaced-apart, outwardly opening channels extend circumferentially about the core. Endless resilient rings are inserted into the channels. A powder-receiving hole is provided in the rearward end of the projectile. When fired, the projectile rides on the resilient rings as it travels down the barrel of the firearm. The core does not come in contact with the barrel, and the resilient rings center the core in the barrel during travel down it for improved accuracy. A rocket-like effect is realized from the rearward discharge of gases liberated by combustion. Also, methods of loading the reusable cartridges are disclosed.

Abstract: Sensors are positioned adjacent a roadway. Such sensors conveniently comprise pressure switches connected to two speed hoses to be run over as in a traffic counter. Alternately, photo-optical, acoustical, or magnetic field sensors can be used. The sensors are spaced a predetermined distance apart in the direction of travel, and provide information to a logic system to measure the speed of vehicles traveling along the roadway. The logic system is connected to a simple readout sign displayed for observation by drivers of vehicles along such roadway, which sign indicates whether a vehicle is traveling at a proper rate, or too fast or too slow, or too close to a preceding vehicle. A modified motion picture camera is provided adjacent the roadway to film a vehicle that is moving too rapidly, and a modified film editing device is provided for counting the frames exposed, and thereby to determine the speed of such vehicle. This latter device preferably reads out direct in miles per hour.