This research sought to improve performance on the M203 grenade launcher through development of a simple, low-cost range estimation device using stadiametric principles. Experiment 1 established the baseline unaided range estimation capability of grenadiers who ere newly weapon qualified. Experiment 2 was a pilot tests of a prototype stadiametric ranging device that used hole sizes scaled to each of 10 man-sized targets located between 50 and 350m from the firer. On the basis of systematic perceptual errors associated wit the original device, corrections to the hole sizes were calculated and incorporated into a corrected device. Experiment 3 compared both devices using experienced soldiers who provided unaided eye range estimations as the baseline. Range estimates with the unaided eye were overestimations of ranges and those with the devices were underestimations. The magnitude of range estimation errors was smaller and showed less variability through use of the devices than with the unaided eye. Outbound targets yielded less range estimation error than inbound targets with the naked eye. In contrast, inbound targets yielded less estimation error than outbound targets for both ranging devices. The influence of direction of target movement on range estimates is discussed in the context of known sources of error in stadiametric devices and design features of the prototypes devices.