SSPH Primus The Singapore Self - Propelled Howitzer 1 ( SSPH 1 ) Primus is a self - propelled howitzer armed with a 155 mm howitzer . Developed jointly by the Singapore Armed Forces ( SAF ) , Defence Science and Technology Agency ( DSTA ) and Singapore Technologies Kinetics ( ST Kinetics ) , it was introduced to the Singapore Artillery in 2004 . " Primus " is derived from the motto of the Singapore Artillery " In Oriente Primus " ( Latin : " First in the East " ) . Production History and Development . The idea for a self - propelled howitzer within the SAF was developed in the early 1990s , with the aim of providing better fire support to the armour brigades in the Combined Arms Divisions . This new weapon system would require the ability to keep pace with the high tempo of armoured operations , while providing the range , firepower and accuracy that the artillery is renowned for . The 155mm self - propelled howitzer was seen as the obvious choice . The decision to develop the Primus was made after a market survey in 1995 and 1996 of some of the world ' s best self - propelled guns from the United States ( M109 Paladin ) , Britain ( AS90 Braveheart ) , Japan ( Type 75 ) and Russia ( 2S3M1 ) found them either too heavy or too wide for local terrain . They were known to have a lot of firepower , were highly mobile and very survivable but they were also very heavy , mostly in the range of 50 tons , and the SAF needed something lighter . The SAF needed the Primus to weigh less than 30 tons and be no wider than 3 metres , for it to move across bridges and through the local vegetation . Hence the decision was made to develop a completely new self - propelled howitzer . Leveraging on its experience with designing , developing and producing various towed artillery systems ( the FH - 88 and FH - 2000 ) for the SAF , ST Kinetics , together with DSTA began the development of the Primus in earnest in 1996 . By April 2000 , the first working prototype was rolled out , using a vehicle chassis adapted from a United Defense armoured chassis ( the " Universal Combat Vehicle Platform " ; UCVP ) which includes components from the US M109 Paladin howitzer , M2 Bradley IFV & M8 - AGS . The next 2 years saw the system undergo a series of comprehensive tests to ensure that the Primus was able to withstand the rigours that were required of it . As land in Singapore is scarce , firing tests were first done at the Waiouru Army Camp live - firing range in New Zealand as part of Exercise Thunder Warrior in February 2004 . The guns have also participated in Exercise Wallaby at the Shoalwater Bay Training Area in Queensland , Australia . In September 2002 , the Primus was officially certified to have met the SAF ’ s stringent criteria , and then being formally adopted into the SAF . Since then , this Artillery platform is utilised by the 21st Battalion Singapore Artillery as their primary weapon system for training and operation purposes . Design . The chassis is based on the proven United Defense M109 155 mm self - propelled howitzer . This has been upgraded in a number of key areas and has a new power pack similar to that fitted to ST Kinetics Bionix infantry fighting vehicle ( IFV ) , which is already in SAF service . The use of common subsystems for the Primus and Bionix IFV offers several advantages , including easier training and reduced logistics . The Primus power pack consists of a Detroit Diesel Corporation 6V 92TIA diesel engine developing 550 hp coupled to a General Dynamics Land Systems HMPT - 500 - 3EC fully automatic transmission . The maximum road speed of the Primus is 50 km / h , with an operating range of 350 km , its combat weight is of 28 . 3 tons allows it to use the SAF ' s current military bridging systems . The Primus could be deployed by the future Airbus A400M Transport aircraft . The turret is fitted with a locally developed 155 mm / 39 - cal barrel with a muzzle brake and fume extractor . This meets the NATO Joint Ballistics Memorandum of Understanding . The range of the Primus ' gun would depend on the type of projectile and charge combination used , but is probably about 19 km with the old M107 high explosive ( HE ) projectile and with an extended range full bore base bleed projectile . In addition to smoke , HE and illumination projectiles , the locally developed 155 mm cargo round can also be fired . A semi - automatic loading system is provided to increase the rate of fire and reduce crew fatigue . The fused projectiles are loaded and rammed automatically ; the modular charges are loaded manually . The Primus has a burst rate of fire of three rounds in 20 seconds and a maximum rate of fire of 6 rounds per min . The bustle mounted magazine holds up to 22 rounds of 155 mm projectile . The digital fire control system automates the complete projectile loading process and gun laying operation . An ammunition inventory management system keeps track of all on board ammunition as well as ammunition expenditure during firing . The weapon is laid to the target using an automatic fire control system , which includes an on board positioning and navigation system . This can receive target information from the battery or regimental command post . It takes less than 60 seconds to come into action and open fire and 40 seconds to re - deploy . Misconception . The Primus has been mistaken as artillery being mounted on a Bionix chassis , and in the earlier days of development as a Bionix MBT variant . This was brought about by the fact that the UCVP ( which the Primus was based on ) bears a superficial resemblance to that of the Bionix and the fact that ST Engineering had indeed at the time been experimenting on a light tank variant of the Bionix .