Terminal ballistics study multivariate behavior and aftermath of projectile and target interactions. Tests and models are often based on monolithic armors, however, layered and spaced armors are common in real world applications. Such configurations add complexities that require research to understand their effects on terminal ballistics. The ballistic limit velocity (V50) represents the speed where armor perforation probability is 50%. It is used for quantitative comparison of protection capabilities for different armors. This research studied the V50 of spaced and layered A36 steel armors against fragment simulating projectiles (FSPs). Four methods for estimating armor V50 were evaluated and compared to experimental data. The first two methods were analytical methods from literature, the third was finite element (FE) simulations in EPIC, and the fourth was a Monte Carlo method developed in this research. The Monte Carlo method using 100,000 iterations was the most accurate and efficient of all methods.