The FBI's new 10 mm cartridge fires a 180-grain jacketed hollow-point bullet at 950 feet per second. This version of the 10mm was tested against 9mm and .45ACP cartridges in a series of trials using gelatin blocks to measure penetration. Based on the 10mm's performance, the FBI recommends it. Whether or not this decision is justified depends upon the cartridge and gun's effectiveness, practicality on the street, and cost effectiveness. Effectiveness or stopping power depends on many factors, including the site of the hit, the target's physical and psychological resistance, and the effects of adrenalin or drugs. The FBI's testing measured only physical effects in gelatin blocks, not real effects on live targets. The test results are far from a guarantee of better effectiveness for the 10mm. Regarding practicality, both the Smith and Glock 10mm pistols are large-frame handguns, making them unwieldy for small officers. If the gun cannot be fired as accurately as a smaller gun, it will be neither practical nor effective. Also, regarding cost effectiveness, a cartridge that scores only 5 percent higher than another, which was the case of the 10mm matched against the .45ACP, with both scoring in the top 10-percent bracket, does not justify discarding the entire inventory of sidearms.