Not to be confused with the G36, this project was part of the early stage of the international Advanced Combat Rifle (ACR) program. Utilizing largely synthetic materials, the HK36 was a very lightweight and compact rifle; with an empty weight of 2.9 kg (6.4 lb.) and a length of 89 cm (35.0 in.). It was equipped with the proven roller-locked delayed blow-back system of the G3. The calibre was 4.5x36 mm, and the muzzle velocity of its 54-grain projectile was a modest 780 m/s. This translated into light recoil and excellent controllability, which allowed the cyclic rate of fire to be as high as 1,100 rounds per minute. To compensate for the moderate striking energy, the projectile contained an asymmetric tungsten carbide core, which provided a devastating effect in soft targets, as well as armour piercing capability.
Another interesting feature in the HK36 was the inclusion of an optical collimator sight. But in 1976, H&K decided to pursue another design as their ACR candidate, and for reasons of economy, the HK36 project was put on the shelf. This other design was the G11 rifle firing caseless ammunition.
The unique magazine door of the HK36 that opened to allow disposable inserts, like the one directly underneath the rifle. This particular rifle is said to be one of the only surviving examples of the HK36 project...
Source post for the text: https://www.hkpro.com/threads/hk36.527812/
Further reading: https://www.thefirearmblog.com/blog/2015/04/13/hks-other-4-6-the-4-6x36mm-hk36/
