Interdynamics MKR assault rifle

schematic drawing of the 4.5 mm rimfire cartridge for Interdynamics MKR assault rifle
Caliber: 4.5x26 mm Rimfire (special ammunition)
Action: blowback
Overall length: 840 mm
Barrel length: 600 mm
Weight: 3.0 kg less magazine
Rate of fire: no data
Magazine capacity: 50 rounds
The Interdynamics MKR assault rifle was another unsuccessful and unconventional design of the Swedish company Interdynamics AB. Interdynamics MKR assault rifle appeared during 1980s on the top of the "micro-caliber" craze. The idea behind micro-caliber (less than 5 millimeters / .20 inch) ammunition was to achieve high velocity, flat trajectory and good penetration in automatic weapon, and with low recoil. The Interdynamics cartridge was based on .22 Winchester Magnum Rimfire cartridge case, with curved taper and 4.5mm / .177" caliber pointed bullet, made of solid brass. Lightweight bullet (1.58 g / ~24.4 grain) achieved a muzzle velocity of about 1000 m/s (3270 fps). The effectiveness of this bullet was claimed to be on par with 5.56x45mm bullet at the ranges up to 300 meters. Unsurprisingly, the stopping power of such tiny bullet was questionable at its best, and use of rimmed, rimfire ammunition obviously compromised the reliability of the rifle. As a result, Interdynamics MKR assault rifle remained only in prototype stage.
Because of the relatively low power of this ammunition, the MKR gun was made using simple blowback system. Rimmed ammunition was fed from semi-circular magazines, located behind the pistol grip, so the overall layout can be classified as bullpup. Ambidextrous charging handle was located at the top of the plastic receiver. Carbine version of the MKR rifle was similar in design, but had shorter barrel.