Rocket-assisted projectiles

High-Explosive Rocket-Assisted (HERA) projectiles M549 and M549A1 were developed to extend the range of standard 155mm guns. With these projectiles, a 39-caliber gun extends its range to 30.1 km.

The projectiles consist of two main components: the warhead, filled with 7.3 kg of high-explosive (M549) or 6.8 kg of TNT (M549A1), and a solid-fuel rocket motor. The rocket section is filled with 3.2 kg of solid propellant. The nozzles in the tail section are covered with a protective cap, which is removed before firing.

The U.S. Army developed the XM1113 rocket-assisted projectile as a replacement for the M549A1. The XM1113 increases the firing range from 30 km to 40 km with a 39-caliber barrel, thanks to a new high-performance rocket motor providing almost three times the thrust, as well as an advanced streamlined external profile for reduced drag. It is also safer due to replacing traditional TNT with an insensitive warhead, which makes accidental activation more difficult.

Rocket-Assisted Projectiles: M549

• Maximum range — up to 30.1 km
• Weight without fuze — 43.5 kg
• Length without fuze — 873 mm
• Shell material — high-fragmentation steel
• Explosive charge:
  • M549: 7.26 kg
  • M549A1: 6.8 kg

The M549 Rocket, as described in the “Kropyva” (Kropyva Fire Control System).

Before firing, the protective cap must be removed from the base of the projectile. If the cap is not removed, the rocket motor will not ignite.

Range table for certain propellant charges:

• M4A2 Charge 7: 19,300 – 19,500 m
• M119A1/A2: 23,500 m
• M203: 30,100 m

Temperature range: -45°C to +63°C