A mechanical acceleration switch has been developed to synchronize instrumentation during a destructive acceleration test. The tests are of short durations and involve very high velocities and accelerations, and a destructive impact. Therefore, accurately synchronized instrumentation is critical. When the switch detects a desired acceleration time history, the switch closes to complete a circuit for instrument activation. Preliminary tests on the proposed switch have shown that switch-to-switch variations exist due to fabrication and assembly tolerances, and that combinations of variations may lead to a switch that does not respond properly. If the switch does not close at the proper time, improper data may be collected; or, at worst, no data may be collected before destructive impact. In this paper, a nonlinear model of the switch closing dynamics is developed in order to investigate the effect of uncertainty on its operation. In particular, the propagation of uncertainty from the switch parameters to the switch dynamics is quantified, and then the design is optimized such that the operation of the switch is insensitive to the variation and uncertainty. The results of the analysis elucidate the parameters that significantly impact switch operation, quantify the reliability of the existing switch design, and ultimately are used to recommend a design that could significantly improve reliability.