Mikoyan-Gurevich MiG-17SN

The MiG-17SN has been one of the most interesting projects carried out by the MiG OKB. The entire project was based on the theory that the use of flexible cannons on a single seat fighter was an effective way to bring your weapons to bear on an enemy aircraft in a fast way, making that only the guns, not the entire aircraft, had to be aimed at the target.
The project involved Mikoyan-Gurevich and Soviet cannon manufacturers Afanasseyev and Makarov. They designed the flexible cannon system that was going to be installed in the fighter. The SN prototype was a standard MiG-17 with a complete redesigned nose which made it 1.069 m (3.5 ft) longer. In order to mount the gun system the frontal air intake was deleted and replaced by bifurcated fuselage sides mounted air intakes.
The SV-25-MiG-17 armament system fitted into the MiG-17 consisted of three TBK-495 23 mm cannons installed in the nose, two on the port side and one on the starboard side. The guns were able to rotate vertically in an arc of  + 27 degrees 26' and -9 degrees 48'. The guns were electrically aimed and had a rate of 250 rounds per minute with the entire system weighing 469 kg (1033 pounds).
Tests at Mikoyan's factory began in 1953 with test pilot G. Mossolov at the commands. The state trials took place on Flight Research Institue (NII-VVS) from 15th February 1954 onwars. The SV-25-MiG-17 system was also installed on an Ilyushin Il-28 bomber in order to train pilots in the use of the turret. The MiG-17SN underwent only three test flights involving air-to-air firings and thirteen flights were executed against ground-based targets.
It was powered by the Klimov VK-1A engine which delivered 6041 lb of thrust power, the same one that powered the MiG-17.
Tests showed that theory and practice differ strongly from each other as they showed the great difficulty to aim the articulated weapons from high speed aircraft. One of the aiming problems was that angles of +/- 10 degrees required a special gunsight. Trials also showed that the MiG-17SN was around 60 km (37 milles) slower than a standard MiG-17. Given the serious aiming difficulties and the performance problems of the prototype, the project was abandoned.

Sources:
1. Signal Squadron - Aircraft In action 125 - MiG-17 Fresco in Action
2. https://en.wikipedia.org/wiki/Mikoyan-Gurevich_MiG-17
3. Salamander Books - The Complete Book of Fighters
4. Midland Publishing - Aerofax - Mikoyan-Gurevich MiG-17 The Soviet Union's Jet Fighter of the Fifties