HIT used to earlier procure 125 millimetre 'blanks' from France for the army's two main battle tanks. Blanks are the final shape of the gun barrel before it is finished. It was then fitted into the tank at HIT.
While Al-Khalid - a joint venture between Pakistan and China - has been with the army since 2001, Al-Zarar is an upgraded T-59 tank.
The country's first blank was produced at the Heavy Mechanical Complex (HMC) in Taxila.
Dawn quoted an official as saying the army had given a go-ahead for the production of 50 125 mm barrels for the two MBTs.
A specialised weapons grade steel was used to manufacture the tank gun. A block of metal is pressed to become a five-metre-long square bar that is forged into a smooth bore 125 mm barrel.
The HIT has finalised a deal for Rs.200 million for the 50 barrels, which is slightly less than the cost of each barrel bought from France.
The official said that after delivering 50 tank guns, the HMC plans to produce artillery guns for the Pakistan Army.