The 155 mm HM41 howitzer was developed to meet the requirements of the Iranian ground forces and in appearance is very similar to the Republic of Korea upgraded M114, which is called the KH179.

A number of facilities in Iran are involved in the manufacture of this weapon including the Hadid Armament Industries Group of the Iranian Defence Industries Organisation (DIO). This facility supplies the 155 mm/39 calibre barrel. The 155 mm HM41 howitzer has been offered on the export market but as far as it is known there have been no export sales of this weapon.

The 155 mm towed artillery system is designated the HM41 and is understood to be an upgraded version of the US 155 mm M114 towed howitzer, which was originally developed before the Second World War.

This fired a standard 155 mm M107 high-explosive projectile, which has been manufactured in Iran for many years by the Ammunition Division of the DIO, to a maximum range of 14,600 m.

The original M114 towed howitzer has been in service with the Iranian Army for many years. By upgrading these with a 155 mm/39 calibre barrel the range of the weapon is increased, allowing it to be deployed more to the rear, so increasing its survivability against counter battery fire.

According to Iranian sources, the 155 mm/39 calibre HM41 weighs 6,890 kg and firing a rocket-assisted High-Explosive (HE) projectile, a maximum range of 30,000 m can be achieved. Firing an unassisted HE projectile, a maximum range of 22,000 m can be obtained.

In 2006 it was revealed that the Ammunition Industries Group of the Defense Industries Organization (DIO) of Iran had developed and placed in production a number of new artillery projectiles which have a significant increase in range when compared to currently deployed conventional artillery projectiles.

This includes a 155 mm HE ERFB-BB artillery projectile which is claimed to have a maximum range of 34 km which is less than some comparable Western-produced projectiles of this type which typically have a maximum range of 39.6 km.

At this time there is no indication that Iran has developed a 155 mm modular charge system (MCS) which is now being increasingly deployed by a number of western countries.

A maximum rate of fire of 4 rds/min can be achieved but there is no load assist device fitted. Elevation range is from 0 to plus 66° with traverse being 25° right and 23.5° left, all under manual control. Direct and indirect fire sights are fitted.

The new 155 mm/39 calibre ordnance is fitted with a double-baffle muzzle brake to reduce recoil forces, with the breech mechanism being of the screw type. The recoil mechanism of the 155 mm HM41 howitzer is of the variable hydropneumatic type. It can be fired using a hand lever or a lanyard. The barrel has a total of 48 grooves.

When deployed in the firing position the HM41 rests on the firing jack under the forward part of the carriage and on the spades attached to the two trails. The system is normally towed by a 6 × 6 10 ton truck which carries a quantity of ammunition (projectiles, charges and fuzes) plus the crew.

Development of this system, which is based on the old US M114 towed artillery system, commenced in 1979, with deliveries to the ROK starting in 1983. Full details of the KH179 are given in a separate entry.

Iran is also now making a 155 mm/45 calibre barrel (the HM47L) but at this stage it is not known as to whether this is installed in a new Iranian towed or SP artillery system or it is a replacement barrel for its currently deployed 155 mm/45 towed artillery systems which have been in service for many years. Iran is also now producing barrels that are chrome plated to extend their lives.

It is now known that Iran is also producing a version of the Russian 122 mm towed howitzer D-30, under the local designation of the HM40. This fires the same family of 122 mm separate loading ammunition as the Thunder 1 122 mm self-propelled artillery system. This is called the 122 mm D-301 howitzer and available details are given in a separate entry.