 Development of tactical nuclear munitions for the type was initiated relatively late in the service cycle of the vehicle, in 1967, and resulted in the 3BW4 round using a 3B4 nuclear projectile with a yield of approx.2 kt.This was improved on three years later with the development of a rocket-assisted 3WB11 nuclear round (using a 3B11 projectile with an RD-14 warhead and propelled by a 3M15 rocket motor).