HK4: Heckler & Koch’s Multi-Caliber Pocket Pistol

Lot 3959 in the September 2019 RIA auction.

The H&K Model 4 was named for the fact that it was offered in four different calibers – .22LR, .25 ACP, .32 ACP, and .380 ACP. The gun came with a complete set of spare barrels and magazines to allow conversion between all of them, and interesting feature not offered by any other pistols like it at the time. The design was by Alex Seidel, one of the founding engineers of H&K. He had familiarity with the Mauser HSc from his time working at Mauser, and it was the rough basis fo the HK4.

The changes between centerfire calibers required nothing more than swapping barrels (and recoil springs, which were pinned to the barrels) and magazines. Differing spring strength for each caliber were enough to make the gun both safe and reliable in the different chamberings. The convert too .22LR rimfire, it was also necessary to unscrew the removable breech face and flip it around. The breech face had two firing pin holes (one centerfire and one rimfire), and the firing pin could pivot enough house either one. When the breech face was removed, the firing pin could be positioned for whichever setting was desired.

The HK4 was interesting and reasonably successful, but never able to really compete with guns like the Walther PP and PPK. During a 16-year production run from 1968 until 1984 a total of 38,200 were made, including 12,400 for the German customs police.


  1. Early production .380″ barrels had longitidunal delay grooves inside the chambers. These were not extraction easining types like P7 since their fronts did not start inside the rifling. They were located roughly at middle section.

  2. I always thought this pistol made very good sense. Especially the conversion from centerfire to .22 LR.

    It would have been especially useful for intel ops requiring a defensive handgun, as ammunition to fit it could be found almost anywhere.

    Not to mention being sort of the ultimate “Fisherman’s Friend” in the tackle box.



    • They are very nice little pistols. I had. The opportunity to shoot one in .380 and .22lr. years ago.

      If they could make it economically enough it would sell well today.

  3. I’ve owned two. The trigger is truly awful.

    The clever cf/rf conversion worked well for me, I’m surprised others haven’t copied it.

  4. Ian. Another very well done and interesting video.

    Harrington & Richardson, the early importer of these HK 4 pistols as you stated, came out with a special two caliber (.22LR & .380), commemorative cased set celebrating their 100 years of operation as they did for many other H&R products in 1971.
    Here are a couple of photos of my example that I acquired many years ago FWIW:



  5. I’ve never seen one of these, but the field stripping and mechanics (other than the caliber conversions) look identical to my .380 Mauser HSc (which I love!). While I’d like to get a PPK also, I see no real advantage to it over the HSc.

  6. I bought one in Hawaii in 1978 but it was just a two-caliber gun–.380 and .22LR. I regret not getting the four caliber kit even though–as noted–it makes “little sense” in .25ACP. I also regretted letting a friend talk me into selling him mine.

    I had forgotten much about it but I do remember the tiny sights and hard trigger. It was manageable when the hammer was cocked but long and heavy and detracted from accuracy in DA mode. I also remember it kicking me harder than my .45 auto. Sometimes my trigger finger would get pinched between trigger and trigger guard. The heel clip release was secure but slow. It was wonderfully compact and didn’t weigh too much.

  7. This kind of field stripping; some little drawing the slide with removable barrel inside and lifting up after delocking the slide retaining latch, is
    going popular novadays with samples like; Bubits BB6, new Mossberg and rotating barrel Glock. The last two have slide retaining element at rear of the slide.

  8. Am I the only one who thinks this and the HSc would be more popular in the U.S. if they didn’t have the heal magazine release?

    • Not sure of “popularity”, but I think the heel release holds the magazine in position more positively. Thumb mag releases are at the mercy of the hole in the magazine which can become worn with use.

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