Body-centered cubic (BCC) refractory metals are widely used in applications where high temperatures, strain rates, and pressures are required. We have developed a new, physically-based BCC strength model that incorporates the effects of temperature, strain rate, and pressure. Dislocation kink-pair theory was used to described the deformation of single crystal BCC metals, and forms the basis of a constitutive framework for predicting deformations in single- and polycrystalline metals. This strength model was implemented in Sandia’s ALEGRA solid dynamics software to enable engineering-scale predictions, e.g. of Taylor impact tests, or high pressure ramp compression tests on Sandia's Z-Machine. We will discuss the foundation, development, and implementation of the theory / model, and present validation of our predictions against available experimental data.