The Center for Electromechanics at the University of Texas (CEM-UT) at Austin has developed two simulations for predicting railgun performance while performing research associated with several Defense Advanced Research Projects Agency (DARPA) contracts. The first predicts the electrical performance of the power supply and the electromechanical performance of the railgun. It is capable of modeling a switched homopolar generator (HPG) charged inductive supply, capacitor storage bank pulse forming network supply (PFN), or a combination of the two power supplies. The s1~cond calculates the railgun's electromechanical performance using the experimentally measured railgun current. Test results from CEM-UT's 1-m long, 1.27 cm square-bore,plasma armature railgun have been used to determine the validity of the aforementioned simulations. Deviation between calculated performance and measured performance is typically less than 5% at railgun current levels lower than 500 kA, however at higher currents the deviation increases. Experimental evidence suggests that the railgun's lack of stiffness and subsequent venting of driving pressure rather than the electromechanical model is primarily responsible for the divergence between predicted and measured results. Additional testing and comparisons are currently being performed with stiffer railgun structures.