Heckler & Koch HK4
semi-automatic pistol
The HK4 is a pocket pistol, first introduced by Heckler & Koch in either 1964 or 1967. It was distinctive for allowing shooters to swap barrels chambered for different cartridges without tools and for having a durable but light hard-anodized aluminum-alloy frame.
Design
The HK4 is largely a refined Mauser HSc self-loading pistol. Heckler & Koch were familiar with the HSc design as many of the Heckler & Koch company founders were employees of the Mauser-Werke Oberndorf A.G. company pre- and post-WW2.
Similar to the HSc, the HK4 utilizes a straight blowback action, with a double-action trigger and a slide-mounted safety. Additionally, the pistol has an internal safety mechanism that will keep the firing pin misaligned from the hammer until the trigger is pulled.
Switching between the three different centerfire chamberings (6.35mm Browning a.k.a. .25 ACP, 7.65mm Browning a.k.a. .32 ACP, 9mm short a.k.a. .380 ACP) merely requires swapping the barrel and recoil spring assembly and the magazine.
This brief starts where responsible research should: with the source description of “Heckler & Koch HK4” as semi-automatic pistol. Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the general reference register because the source frames it as semi-automatic pistol. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jun 21, 2026. The linked authority identifier is Q383837. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 1964 and 1967.
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This entry incorporates text from “Heckler & Koch HK4” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.