Initially, the practice was to load every 5th round as tracer. The problem with this was that the tracer rounds have different ballistics than the non-tracer rounds (is this modelled in AH, HT?), so that at longer ranges, if your tracers were on target, 80% of your gunfire was missing the target. The practice of putting five or ten tracer rounds together near the end of the belt as a warning that you're low on ammo also bit both ways, as it also warned your target that you were running low. Units that stopped using tracers saw their success rate almost double and their loss rate drop.