the barrel which engaged similar grooves in the interior of the slide. SIG licensed this design in 1947. The SIG Sauer design went further by having no grooves in the slide or barrel. Instead an enlargement of the chamber locks directly on the ejection port of the slide. The double action / single action (DA/SA) trigger design of the P220 is also a SIG Sauer innovation similar to the J.P. Sauer & Sohn 38H pistol. Further design refinements include a hammer decocking lever and positive firing pin block safety. Instead of the locking lugs and recesses milled into the barrel and slide of Browning-derived weapons such 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. The SIG Sauer System (embossed on the side of the Browning BDA) is a refinement of the Petter-Browning system. 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 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-anodized coating. 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 features an automatic firing pin block safety which is activated by the trigger mechanism, similar to the one used in the Czech CZ-038 from the period after the Second World War. 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 user chooses to manually cock the hammer. Double-action trigger pressure is measured at approximately 12–14 pounds, with subsequent shots being fired in single-action mode with a lighter trigger pressure of approximately 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