This gun was originally called the "HK54" by its manufacturer
(Heckler & Koch). It's first major purchaser was the West
German Bundesgrenzschutz (Paramilitary Border Police)
who called it the "MP5" to fit with their system of cataloguing
weapons in their armoury. The MP5 name became so popular that
eventually Heckler & Koch followed the trend and renamed the
gun "MP5" in their product catalogues. So strictly it's not
right to call it an "HK". It has many popular names. The
British Army nickname for it, for example, is a "Hockler".
The gun in the link is indeed a Sten Mk II silenced machine carbine.
Unfortunately the sten is not a particularly good gun. It had
many derogatory names during the war; ""StenCH gun", for example
or "Tuppeny Woolworths gun". Its various iniquities included,
mags that either would not fit or which would fall out, a fore
end that would incinerate the firers hand if not careful,
ammo feed problems if the magazine was held while firing,
mag springs that would jam if fully loaded with 32 rounds
and so on...
Also in the "Hidden and Dangerous" game is featured the "de Lisle
Commando Carbine" ; essentially a Lee Enfield rifle rebarreled
to fire .45" ACP rounds through a fixed silencer. It was a
remarkable weapon by the standards of its time. It was silent
at 30 yards and could kill at 400 yards!
Since the MP5 fires from a closed bolt this raises questions about
the possibility of "cook off" where the bore heats up sufficiently
to cause rounds to detonate prematurely. In practise, however,
with the MP5 this is impossible to achieve under any remotely
likely set of circumstances.
The problem with the SD variants of the MP5 is that some regard
them as underpowered. This may well be so but it does not appear
to overly concern such elite military units as the US navy SEALS,
British SBS or the French Foreign Legion CRAPS who all include
this weapon in their inventories.
The best model representation of the MP5 I have seen in a game so
far is in the excellent "Rainbow Six 3" series.
.