For what cartridges has the HK MP5 been chambered
Executive summary
The HK MP5 family began as a 9×19mm Parabellum submachine gun but, over decades, Heckler & Koch and third‑party makers have produced MP5‑pattern weapons in a wide range of calibers including 9×19mm, 10mm Auto, .40 S&W, .22 LR, .45 caliber variants, and even rifle cartridges in earlier HK development work (notably 7.62×51mm, 7.62×39mm and 5.56×45mm prototypes that predate the MP5 itself) [1] [2] [3]. Reporting and manufacturer materials show a mix of official HK chamberings, authorized rimfire reproductions, and later commercial conversions and clones — together creating the diverse caliber list commonly attributed to the MP5 family [4] [3] [5].
1. Origins: rifle‑caliber development that led to the MP5 name
Heckler & Koch’s naming and development history begins with roller‑delayed rifles in full‑power rifle calibers; early HK types were built in 7.62×51mm NATO, 7.62×39mm M43, and 5.56×45mm NATO before HK created a selective‑fire carbine in a handgun cartridge which became the MP5 as the HK54 in their system — a clear reminder that the MP5’s lineage includes rifle calibers even though the production MP5 family is centered on pistol cartridges [1].
2. The canonical cartridge: 9×19mm Parabellum
The defining and most widespread chambering for the MP5 is 9×19mm Parabellum; the MP5A3 workhorse on museum displays and the majority of military and law‑enforcement procurement are in 9mm, and parts, magazines and literature overwhelmingly reflect 9mm as the standard [2] [5] [6].
3. Larger pistol calibers: 10mm, .40 S&W and “.45 caliber” variants
HK and other suppliers produced MP5 variants in larger pistol calibers: commercially and in contract form the MP5/10 (10mm Auto) and MP5/40 (.40 S&W) exist, and some sources assert MP5‑pattern models chambered in “.45 caliber” and other larger handgun rounds have been produced or offered [2]. These chamberings were generally niche, marketed for higher stopping power, and not as ubiquitous as the 9mm models [2].
4. Rimfire and semi‑auto reproductions: .22 Long Rifle
Heckler & Koch authorized rimfire MP5‑style rifles in .22 LR through partnerships (Umarex/HK USA) to give civilian shooters the look and handling of an MP5 in a low‑powered, semi‑automatic package; major retailers list .22 LR MP5‑branded models as current commercial products [3] [7]. These are faithful externally but are rimfire, semi‑auto designs rather than military full‑auto MP5s [3].
5. The SD and suppressed variants keep the same chamberings
Specialist models such as the MP5SD (barrel with integral suppressor) are primarily 9×19mm designs that incorporate baffled/ported barrels and a sealed outer sleeve to reduce sound and velocity; these variants illustrate how HK adapted the platform for different mission sets without changing the core cartridge in standard production lines [4] [1].
6. Magazines, aftermarket and clone influence on reported calibers
A large part of the apparent variety of MP5 calibers in market listings and forum threads is driven by clones, aftermarket conversions and accessory markets: parts suppliers and clone makers produce MP5‑pattern guns and magazines in multiple calibers, and commercial listings and forum inventories reflect that ecosystem as much as HK’s own official catalog [6] [5] [8]. This creates a reporting halo in which non‑HK or limited‑run chamberings are treated interchangeably with factory models.
7. Limits of available reporting and implicit caveats
Primary sources here (HK’s product pages, museum descriptions, authorized rimfire marketing, museum/collector writeups and community forums) together document 9×19mm as primary and show official/authorized examples of .22 LR plus documented 10mm, .40 S&W and “.45 caliber” offerings, while historical HK development included full‑power rifle calibers that preceded the MP5’s pistol‑caliber form [4] [3] [2] [1]. The supplied reporting does not provide a single, definitive canonical list of every prototype, one‑off conversion or importer‑specific chambering worldwide, so claims about exhaustive experimental or clandestine chamberings cannot be substantiated from these sources alone (p1_s1–[1]2).