Ballistics as well as socio-political and budgetary factors must be taken into consideration when choosing a law enforcement weapon. The guideline for effective police service arms has been the ability to disable a felon with one shot into the torso. But the police administrator must also consider how his choice conforms to the community's perception of appropriate force. The first modern 10mm auto pistol round was publicized in 1972; the first experimental rounds consisted of a .30 Remington Auto rifle shell case, cut off and straightwalled to allow seating of a .401 diameter .38-40 Winchester bullet. Other guns were designed in this timeframe which were unusually powerful. However, police buyers are most interested in factory-ready 10s such as the Colt Delta and the new Smith & Wesson 1006; most U.S. makers have one or more 10mm Auto cartridge on the market. The FBI specifications, which many other agencies will follow, require a change from the DA Walther-pattern slide-mounted hammer-drop safety to an Erma-type DA with cocking-decocking lever usable by either hand (a perennial argument which concerns the safety/liability aspect of the arms issue), a quantity of compacts in 10mm with the same control pattern, and a pistol that can handle full-power 10mm ballistics. Both the Delta and the S&W can be compared with four-inch .41 Magnum revolvers in power level; the most serious area of wear was peening of the disconnector cut in the Delta's side. The 10mm rates high in all three key qualities of handgun stopping power: energy transfer, momentum transfer, and sectional density/ballistic coefficient. It is also a good platform for launching pellet-filled, high-velocity "safety" frangible-bullet rounds. In short, the 10mm pistol's ballistics, combined with the semi-automatic system, provides law enforcement officers a high degree of tactical utility. 1 table.