POTD: The Heckler & Koch HK4 – Four Guns in One

Welcome to today’s Photo of the Day! Here we have where it all started for one of the biggest names in guns. This is the Heckler & Koch HK4, the very first pistol H&K ever built. By the early 1960s they’d made their name turning the roller-locked CETME into the G3 battle rifle, and a pocket pistol was the logical next step into the commercial market.

The “4” isn’t random. This little blowback gun could be chambered for four different cartridges: .22 LR, .25 ACP, .32 ACP, and .380, and swapping between them took nothing more than a new barrel, recoil spring, and magazine. Going from the centerfire calibers to the rimfire .22 meant one extra trick: you unscrewed the breech face and flipped it around so the firing pin lined up with the rim instead of the center. That’s clever work for a gun this small.

There’s a good reason it sold in Europe. Plenty of countries cap how many guns you can own, and one pistol that shoots four calibers counts as exactly one. The design leaned hard on the old Mauser HSc, which makes sense; H&K’s founders were ex-Mauser men, and Alex Seidel, who led the HK4, had designed the HSc himself. It never quite caught the Walther PP, but it got H&K into the pistol game.

Most of our POTDs utilize images from our friends at Rock Island Auction Company, the premier firearms auction in the United States. Take some time to browse their current auctions – who knows, maybe you’ll find a piece of history to take home!

“Heckler & Koch Model HK4 Semi-Automatic Pistol with Box.” Rock Island Auction, www.rockislandauction.com/detail/5032/1204/heckler-koch-model-hk4-semiautomatic-pistol-with-box. Accessed 25 June 2026.

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