Why do all modern tanks have smoothbore main guns? General Leave a Comment on Why do all modern tanks have smoothbore main guns? The Challenger 2 has a rifled 120mm gun. The Challenger 3, announced in 2021, has a smoothbore 120mm. Why? Why did Britain take so long to make the big switch? What are the real advantages of each type of armament? (Visited 2 times, 1 visits today)