The HK4 was HK's first commercially successful pistol, a DA/SA blowback compact convertible between .22 LR, .25 ACP, .32 ACP, and .380 ACP with interchangeable barrel and magazine sets. Its convertible design and reliable DA/SA action established HK's commercial reputation before the P9S and USP era. Type: Pistol Action: Semi-Automatic Caliber: .22 LR Capacity: 8 Year introduced: 1968, Germany Weight: 16.5 oz Overall length: 6.3" Status: Discontinued Intended use: concealed_carry, collector, historical