New weaponry headed for the UK's incoming Challenger 3 tank has entered production.
Two smoothbore L55A1 120mm guns will be tested in Germany before integration with a new, fully digital turret in the UK.
The smooth design differs from rifled weaponry, which has traditionally seen accuracy increased through grooved barrel interiors.
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As munitions have developed, though, the desire for rotational spin applied to projectiles has decreased – smooth barrels capable of firing newer rounds.
The plan is to fit these proven German guns into next-generation turrets, before fitting the turrets into older Challenger 2 hulls.
Experts have questioned whether this integration could cause delays to the tank programme similar to those previously seen in the cancelled Warrior, which required similar transformations.
As the Ministry of Defence's (MOD) "troubled" Ajax programme also looms, the Challenger 3 weapons are currently ahead of schedule through the German contingent of Challenger 3's RBSL developers, Rheinmetall.
The joint effort also features British engineers from BAE Systems Land.
Steel has been cut in the Unterluss facility in Germany, but the completed smoothbore guns will head for RBSL's UK base for turret integration.
Watch: Could Challenger 3 tank upgrades be cancelled like Warrior's?
Recent years have seen Germany gain far more experience than the UK in main battle tank production, especially through the development of the Leopard.
Now, the allies have come together to develop a British capability that can keep pace with other systems in NATO, and share the same tank rounds used by alliance members.
Colonel Will Waugh, Armour Main Battle Tank Programme Director, said: "This is another and early step forward on the path to delivering a genuinely world-class MBT for the British Army.
"Pairing the tried and tested L55A1 smoothbore gun with the latest kinetic energy ammunition and programmable secondary natures will give CR3 a step-change in the lethality over CR2.
"The move to a smoothbore gun brings the UK in line with its principal NATO allies increasing our interoperability and ensuring access to the latest ammunition natures. This will future-proof CR3's lethality against the full range of threats until its OSD."