Rifle power in a submachine gun package, the HK53. It is truly neither rifle, nor submachine gun, but a strange mixture of both. A submachine gun is defined as a select fire weapon, fired from the shoulder using a pistol cartridge. However, with only an 8.3 inch barrel, the HK53 hardly qualifies as a rifle. The HK53 fills the void where pistol cartridge submachine guns like the MP5 or MP5/10 and MP5/40 may not be suitable against armored suspects.
Many parts of the HK53 are interchangeable with the MP5, they are so similar in size. The example above shows us the newer style concave buttplate that until recently was only reserved for the MP5 series. It is now available for the 33 and 53 series. The forks are slightly longer on this model than for the MP5 series. The four prong flash hider seen here is now standard. It does much more to suppress the flash from this short barreled weapon than did the more standard flash hider seen on the 33 and G3.
There is also a frangible ammunition adapter offered as an option that provides the necessary back pressure to cycle the HK53 reliably with very light .223 caliber frangible ammunition that is now available for entry situations where deep penetration is more undesirable. This may prove somewhat unnecessary, since the national trend of adopting .223 caliber firearms for tactical entry is proving that there is generally less ancillary penetration of conventional .223 caliber projectiles than even pistol caliber submachine guns.