Abstract: In the design of Weapon Control Systems (WCS) for main battle tanks there is a requirement for low-order models of the elevating mass and barrel. In this work two models suitable for this requirement are put forward. The two models under consideration break the barrel down into rigid sections that are connected by frictionless pin-joints and linked by torsional springs and dampers. This model is referred to as a Lumped Parameter Flexible Beam Model (LPFBM) in this work. These models consider the barrel being broken down into two and three rigid sections. The lengths of the rigid sections and spring stiffnesses are selected to preserve the resonances (poles) and anti-resonances (zeros) of the system. This is achieved by using a novel scheme based on equations derived for the cantilever mode frequencies for the zeros and on optimising the lengths of the rigid sections for the poles. The responses from these two models, in the frequency and time domain, are compared to a finite-element barrel version, which is used as the base model and a non-optimised two-section LPFBM. Recommendations are then made on the appropriate model to use in the design of a WCS based on the required frequency range of the model and whether muzzle motion predictions are needed.