We've used ours at 1188 yards and 1760 yards, both times on a full-sized 3/8" AR500 IPSC. At 1188 yards, the terrain from the firing line to the target was pretty flat. We could detect hits without any problem through optics with a 16" .308, 6 Creed, and 6.5 Creed. If you were looking for it you could see the red light with the naked eye. However, at 1760 yards, seeing the flashing red light was very inconsistent. We were shooting 6 Creed and 6.5 Creed at that distance and there were numerous times when we did not see any flashing red light, and that was with at least 2 or 3 people spotting in addition to the shooter. We were surprised when we went down range and saw many more impacts than we saw red flashes. We think part of the reason for this is that the terrain from the firing line to the target was elevated as we placed the target on a hill. Since you have to be aligned within 18 degrees of the front of the prism for best results, we assume we were outside that 18 degrees or where we impacted the target with our rounds lacked the energy to set off the Magnetospeed. When we were aligning the Magnetospeed, since the firing line was so far away and at a different elevation, we were just kinda guessing where the firing line was and guessing whether or not we were aligned. In hindsight we should've used radios to set off the Magnetospeed and communicate visibility with the firing line.