You’re all familiar with the MP5 and probably all familiar with the G3 too. I’d imagine a few know about the older 556 guns from HK but I reckon quite a lot could be unfamiliar so let’s discuss them briefly.
As a succinct history, the roller-delayed blowback system HK is clasically known for was derived from the MG-42 during WW2 and ended up doing very well in the G3 series of rifles that was developed by the Germans and Spanish in the 1950s to fire the 7.62x51mm NATO cartridge. Realising they were on to a good thing, HK expanded the line in the 60s with designs firing Russian 7.62x39mm, the infamous 9x19mm and also in 5.56x45mm NATO.
Very few of the guns were made firing the Russian rounds and the 9mm guns you already know about, but the 556 weapons were made in fairly significant numbers and used by various forces alongside significant commercial sales, yet aren’t often seen in games or films and aren’t particularly well known comparative to their production numbers.
In this short clip I put some bursts through an HK-53 though the longer barreled HK-33 is the father of the family (both in 556). They operate, handle and function just like an MP5 or G3 with the same types of iron sights, optics mounting options, control configurations and modulariuty in terms of quickly removable stocks, handguards and lower receivers via the classic HK pins.
The HK-33 did try to give the M16 a little bit of competition in the US and the shorter -53 was apparently more reliable than the early short barreled ARs, something you’ll find out if you watch the videos published that cover these guns via Forgotten Weapons. Early attempts at compressing the M16 down to 11.5″ or shorter barrel lengths suffered somewhat with reliability as they hadn’t dialled in the gas system and ammunition at the time, but of course the HK has no gas system and would understandably fair better in this regard. Magazine options for the 556 HK guns were also slightly better than for the ARs at the time in some respects with HK putting out reliable steel 40 round mags and plenty of 30 rounders.
The recoil on these guns is noticeably more than on most typical ARs, though certainly not to the point of making them impractical or unpleasant to shoot in any way. The selectors aren’t quite as quick or easy and its’ the same story with changing magazines, but again, fairly minor issues. It’s just that if you have a well built, reliable AR with good mags and ammo then you’ll have a gun that is overall a better option compared to the HK.
Personally I first handled an HK-53 going through my Weapons Tech training in 2008 as those carbines were used by RAF aircrews before standardising on L85s and L22 carbines. You can check wikipedia for the suprisingly extensive list of military and police forces that adopted the HK-33/53 and variants thereof over the years. Not a gun that’s popular today and for fairly good reason but certainly an interesting and prominent note in firearms history that many might not be aware of.