SIG Sauer P220 - Design

Design

The P220 operates by the locked breech short-recoil method pioneered by John Browning. On firing, the slide and barrel are locked together until, after a few millimetres of rearward movement, the barrel is cammed down at the rear after the pressure has dropped enough when the bullet has departed the barrel, whereupon the slide completes the rearward stroke ejecting the spent cartridge. The recoil spring then propels the slide forwards, stripping a round from the magazine, and in the last few millimetres of forward movement, the barrel is cammed upwards at the rear, locking the slide and barrel together again. Instead of the locking lugs and recesses milled into the barrel and slide of other Browning-type weapons as the Colt M1911A1, Browning Hi-Power and CZ 75, the P220 variants (and many other modern pistols) lock the barrel and slide together using an enlarged breech section on the barrel locking into the ejection port. This simplifies manufacture but has no functional disadvantages. The slide of the P220 series is a heavy-gauge sheet metal stamping with a welded-on nose section incorporating an internal barrel bushing. The welding is so well-executed it is almost impossible to detect. The breech block portion is a machined insert attached to the slide by means of a roll pin visible from either side. The frame is of forged alloy with a hard-anodised coating. While designed for ease of production, the SIG 220 series is of the highest quality and there is no compromise in durability or functionality compared to pistols produced using more traditional methods. The SIG P220 series incorporates a hammer-drop lever to the rear of the trigger on the left side, which first appeared on the Sauer 38H before World War II. After chambering a round, the hammer will be cocked, so for safe carriage the hammer drop is actuated with the thumb, dropping the hammer in a safe manner. The P220 also introduced a firing pin block safety which is activated by the trigger mechanism—similar to the one used in the Colt M1911's Series 80 pistols. The pistol may now be holstered, and can be fired without actuating any other controls. The first shot will be fired in double action mode, unless the firer chooses to manually cock the hammer. Double action trigger pressure is around 12–14 pounds, and subsequent shots will be fired in single action mode with a lighter trigger pressure of around 6 pounds. There is no separate safety lever to manipulate; the hammer drop is the only manual safety device. As with other double action pistols such as the Walther P38 and Beretta 92F, some training is required to minimize the difference in point of aim caused by the different trigger pressure between the first double action shot and subsequent single action shots when the hammer is cocked by the rearward movement of the slide, but this is easily overcome.