Assisted projectile

A Rocket Assisted Projectile is an artillery or cannon round incorporating a rocket motor for independent propulsion. This grants the projectile both greater speed and range than an ordinary shell, which is propelled only by the ballistic force of the gun's exploding charge. Some forms of Rocket Assisted Projectiles can be outfitted with a laser-guide for greater accuracy.

The North Korean M-1978 / M1989 (KOKSAN) 170mm self-propelled gun can use rocket assisted projectiles to achieve a range of around 60 kilometres (37 mi); at one time this was the world's longest range artillery piece.

When NATO standards required member armies to have corps-level artillery that could fire to a minimum range of 30,000 metres (19 mi), nearly all member nations solved the problem with RAP rounds in their 155 mm (6.1 inch) artillery. The Belgian Army was the only NATO member army that did not require RAP, reaching the required range with a conventional round.

...
Wikipedia