It also has a wide selection of ammunition types. Comparisons of muzzle velocities of the 4-inch pistol and the 16.5-inch carbine revealed only a 6 percent increase in velocity with the carbine; any muzzle velocity gain depends on the powder's burning characteristics. The average 9mm hollowpoint increased in energy by just 50 foot-pounds. Compared to the pistol, the average carbine-fired hollowpoint produced slightly less penetration and had a slightly smaller recovered diameter. Based on tests of 12 hollowpoints, the 9mm pistol and the 9mm carbine produced the same average estimated wound ballistics. However, police officers can enhance the effectiveness of the 9mm by careful bullet selection. The carbine barrel length does not improve the interior, exterior, or terminal ballistics of many popular hollowpoints at all, but the carbine barrel length does push some 9mm hollowpoints into the .357 Magnum bracket in terms of velocity, energy, wound ballistics, and tactical penetration. Photographs and table