M1 Tank 120 mm Main gun placed on demo medium tank at a little over half the weight

General Dynamics Land Systems (GDLS) on 3 October unveiled a medium-weight tracked vehicle demonstrator called the Griffin that meshes elements of the turret and 120 mm cannon from the company’s M1A1/M1A2 Abrams main battle tank (63-72 tons) with its Ajax Scout Specialist Vehicle.

The Ajax Scout is a 38-42 ton light tank developed for the UK by General Dynamics

SOURCES- IHS Janes, Wikipedia, General Dynamics