Work on this system began in 1968 and first prototypes were showen on the millitary parade in 1975, and production began in 1980. The system is mounted on the FAP-2026 6x6 configuration truck, with the trigering system activated 50 meters from the tube. It posseses 32 tubes, and reserve loading on the automatical charger another 32 missiles. The M-77 missile is a standard explosive warhead missile, weighting 67.10 kg, with the 19.53 kg warhead consisting of explosive TNT, Aluminium powder and Hexogen. In the M-77 missile warhead are 2562 103gr weight steel balls and 430 443gr weight steel balls. The missile speed is 750m/s. 32 missiles are covering elypse 167x213m. The new M-91 missile is a cluster type-warhead, consisting of 48 small bombs with cumulatiwe and fragmental action. The second type of cluster warhead consist 4 anti tank mines. M-77 MLRS was used in civill war in Yugoslavia, prooving its firepover and thrust.

Even though most of Iraq's missile production facilities received heavy damage during the Gulf War, Baghdad maintains some of the equipment needed to produce ballistic missiles, in part because of the dual-use nature of much of the equipment required for producing SCUDs. Today, Iraq's production efforts are focused on developing the Ababil-100, with an estimated maximum range of 150 kilometers, and the Ababil-50, a Yugoslav-designed 50-kilometer range battlefield artillery rocket that has been identified as derived from the M-77 Oganj 128mm MLRS.

The M-77 128 mm (32-round) 'Oganj' (Fire) was developed in the early 1970s to meet the operational requirements of the former Yugoslav Army. It is normally found in batteries of six launchers. It performs a similar role to the former Czech 122 mm RM-70 (40-round) MRS.

It does not, however, have an armoured cab or the excellent cross-country performance of the Czech vehicle, which is based on the Tatra 813 (8 × 8) truck chassis.

The M-77 128 mm MRS basically consists of a modified FAP 2026 BDS/AV (6 × 6) series cross-country truck with a 32-barrel 128 mm rocket launcher mounted at the immediate rear of the chassis and an additional pack of 32 rockets to the rear of the cab for rapid reloading. The launcher fires a 128 mm calibre, 2.6 m long unguided solid-propellant rocket to a maximum range of 20,600 m.

Weight of the rocket is 67 kg. The 19.5 kg warhead contains 2,562 steel spheres 6.35 mm in diameter and 930 steel spheres of 10.32 mm diameter that are lethal out to a radius of over 30 m. The explosive content is 3.8 kg and a fuze with preselected super quick, inertia and delay action options is fitted as standard.

The rockets are either launched singly or in a ripple salvo, the latter taking a total of 25.6 seconds. The rockets can be launched either by manual, semi-automatic or fully automatic control with an optional 25 m off-vehicle remote-control box cable system. Once the 128 mm rockets have been launched, the launcher is traversed to the rear and depressed to the horizontal, the pack of 32 rockets to the rear of the cab is raised until it lines up with the launcher and the rockets are pushed into it. The reloading system then goes back onto the floor of the truck and the launcher is traversed forwards ready for firing again.

The complete reloading sequence takes 2 minutes with the second salvo capable of launch within 5 minutes of the first. Reloading can also be performed manually. When travelling the launcher is lowered and the launcher and reloading pack are covered by a tarpaulin that is folded up under the rear in the firing position. The time required to occupy or leave a firing position is less than 20 seconds, with the time taken for occupying a position, firing both rocket loads and leaving being 4 to 5 minutes in total.

It is believed that the original FAP-2220 BDS (6 × 4) chassis was used only for early production vehicles as it is not suitable for travelling across very rough country because of its low ground clearance. The chassis was then changed to the FAP 2020 BS (6 × 6) and FAP-2026 BDS/AV (6 × 6) cross-country trucks. These vehicles have large tyres with single rather than dual rear wheels and are fitted with a central tyre pressure-regulation system that allows the driver to adjust the ground pressure to suit the type of ground being crossed. Recent information has indicated that production of this system and its chassis was completed some time ago.

This is a Bosnian version which, instead of having 32 × 128 mm rocket tubes, has 2 × 4 128 mm barrels and 2 × 2 122 mm barrels. The latter can launch standard 122 mm unguided rockets of Russian or equivalent types which are widely available.

To complement the M-77 there is a 128 mm lightweight single-tube rocket launcher for use by commando, special forces and territorial defence units.

In addition to being used by Serbia, this 128 mm single-round launcher is known to be used by Macedonia (60 units) and Slovenia (56 units).

The Croatian company of RH ALAN has marketed a very similar system to the M-77 Oganj but based on a more mobile Tatra (8 × 8) chassis called the 122 mm (32-round) M96 Typhoon. In addition to having greater mobility it has the added advantage of firing the more widely used Russian family of 122 mm unguided artillery rockets. As far as it is known the Croatian system has not been exported. Full details are provided in a separate entry.

This appears to be a modified version of the M-77 Organj 128 mm system. It is believed that seven systems are in service with the HV.