The 155 mm Gun M46/84 is a conversion of the Russian 130 mm Gun M-46 (or the Chinese North Industries Corporation Type 59-1) to accommodate a new 155 mm 45 calibre barrel capable of firing Extended Range Full Bore - Base Bleed ammunition of the separate loading type (projectile and charge).

This conversion gives a range increase of 45 per cent over the original 130 mm M-46 when firing ERFB-BB ammunition. The efficiency of the 155 mm ERFB projectile is claimed to be about three times that of the older Russian-designed 130 mm OF-482 projectile.

It is believed that this upgrade package was originally designed by the former Space Research Corporation headed by the late Dr Gerald Bull. The converted gun M46/84 was also sold to Iraq, but it is understood Iraq did not carry out any upgrades on its existing fleet of weapons prior to the Gulf conflict of 1990/1991.

The M46/84 conversion involved replacing the existing 130 mm barrel with a new 155 mm barrel 45 calibres long. This is designed to make use of the original 130 mm sliding breech and cradle parts.

The barrel is fitted with a high-efficiency double-baffle muzzle brake of a new design. An updated equilibrator sealing system is introduced, involving a nitrogen pressure adjustment and an updated sealing system for the recuperator mechanism is also required.

The existing 130 mm M-46 sights are also revised to accommodate the new 155 mm ballistics with the optical sight graticule being changed. A new range quadrant drum with respective range scales is mounted.

The converted gun could also be delivered in 152 mm calibre with this model being designated the cal. 152 M46/86. It uses the same system of propelling charges and Serbia and Montenegrin projectiles M84 and M84-GG. Maximum range with the M84 projectile is 27,500 m and with the M84-GG base bleed it is 34,000 m. The 152 mm model also has a 45 calibre barrel.

At the request of customers, both versions of the converted gun could be supplied for the use of ammunition with separate loading propelling charges.