NORINCO rolls out SM4 120 mm mortar vehicle

01 July 2016
The latest Chinese SM4 120 mm self-propelled mortar is based on a 6×6 WMZ-551 amphibious armoured personnel carrier, which is seen here in its ready to fire configuration with roof hatches open and mortar traversed to the front. Source: NORINCO

China North Industries Corporation (NORINCO) is exporting a new 120 mm mortar version of the widely deployed 6×6 WMZ-551 amphibious armoured personnel carrier (APC) designated the SM4 120 mm self-propelled mortar (SPM).

The crew and diesel engine compartment is located at the front and for its new mission the roof line of the WMZ-551 has been raised towards the vehicle’s rear to provide greater internal volume for the 120 mm muzzle-loaded mortar and its ammunition.

The driver is seated front left with the commander to the right and above the latter position is an unprotected pintle-mounted 12.7 mm machine gun (MG).

NORINCO is now marketing a number of remote weapon stations (RWSs) and one of these could potentially be fitted in place of the 12.7 mm MG to enable the weapon to be fired from under armour and environmental protection.

For use in high ambient temperatures an air-conditioning system is fitted as standard and the fully amphibious capability of the standard 6×6 WMZ-551 APC is retained.

With little preparation the WMZ-551 SM4 120 mm SPM is fully amphibious and propelled in the water by a shrouded propeller fitted one either side at the rear that enables the vehicle to reach maximum swimming speed of up to 8.5 km/h.

The system has a crew of five, including the commander and driver and NORINCO is quoting a gross vehicle weight of 17 tonnes including ammunition, and a maximum road speed of up to 100 km/h.

The 120 mm mortar is fitted with a specially designed recoil system to reduce the stress on the platform so that no stabilisers are required to be deployed before the weapon is fired.

The weapon is coupled to a computerised fire-control system (FCS) that enables the system to come into action, carry out a fire mission and then redeploy before the arrival of counter battery fire.


WMZ 551 6×6 wheeled armoured vehicle


During the early 1980s a whole array of Western multi-wheeled APCs started to appear, possibly influenced by older designs like the Soviet BTR series and the Swiss Mowag Piranha among other influences. There was a general tendency towards 4×4 – 6×6 rather than huge 8x8s with some extra versatility and agility but still potent weaponry (toward the APC/IFV category) and the French Renault\’s VAB in 1979 and the SANDF Ratel are good examples. So far that it inspired the Chinese Type 92 and the Indonesia Anoa (Pindad) Panser (and both are often compared). Norinco\’s WZ 551 however was not a faithful copy of the VAB, being significantly larger but apparently not heavier. Development started in 1985 and ended with the Type 90 followed by the Type 92 of which the first entered service in 1995. While around 2000 (according to the Chinese wikipedia) had been cranked up for the PLA alone, around 200 had been exported throughout 15-18 countries until today.


WZ551 6×6

Prototypes includes the pre-production vehicles, the WZ551-1 (73 mm sb gun), WZ554 SPAAG with twin 23 mm autocannons, WZ551D PL-9 surface-to-air missile system and Yitian SAM and the 4×4 WZ91 HJ-8 ATGM tank hunter. Apparently a 120mm self propelled mortar (similar to the BTR-80 based 2S23 NONA-SVK) and a 122 mm self propelled howitzer versions were also produced, the latter being the sole 8×8 version. Both will be treated as separate subjects since they only have the chassis in common.

Sri Lanka Army WZ551B APC as of 2012Sri Lanka Army WZ551B APC as of 2012

Chinese WZ551/Type92 APC specs.

Dimensions 6.63 x 2.80 x 2,80 m
(21.7 x 9.1 x 9.1 fts)
Total weight, battle ready : 12.5 to 14.9 tonnes fully loaded
Crew 3+9 (Commander, Gunner, Driver, 9 troops)
Armament 25 mm AC QF, 400 rounds (IFV) + 7.62 mm coax
or 12,7 mm HMG 1500 rds (APC) + 7.62 mm coax. See notes.
Armour Overall 12.7 mm ballistic protection (0.5 in).
Propulsion Deutz TD 8 cyl. 320 hp
Top speed 85 km/h (53 mph)
Range 600 to 800 km (500 miles)
Suspension Independent 4×4 or 6×6 WD
Total production Unknown – 1,000 to 2,200 range

WZ551-Type92 APC


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