Interdynamics MKR

The Interdynamics MKR was a Swedish prototype assault rifle developed in the 1980s.

Design
The Interdynamics MKR was originally designed using a 4.5x26mm Rimfire round using solid brass bullets. Its purpose was to provide a flat ballistic trajectory along with armor piercing capabilities with low recoil for the user to handle, even when fired fully automatically.

Another interesting feature about the weapon is that it was bullpup in design, which means that the magazine is located behind the trigger, and also utilized the blowback system of operation. The bullpup design was a significant tactical advantage because it increased the firearm's compactness and allowed for a smaller, lighter and more efficient firearm.

Ammunition
An additional part of the concept was for it to use a low cost ammunition type. The 4.5x26mm MKR round was claimed to be ballistically as effective at 300 meters as the 5.56x45mm NATO round.

The weapon never proceeded beyond prototype stages.