Base bleed is a system used on some artillery shells to increase their range, typically by about 20–35%.Since base bleed extends the range by a percentage, it is more useful on longer range artillery where an increase of approximately 5–15 kilometres (3.1–9.3 mi) can be achieved. Until the late 1980s the small gains in range were not considered worthwhile for field artillery. Base bleed shells are becoming more common in units equipped with modern artillery which have far greater range than the old ones, but are usually only used at close to, and beyond, normal maximum ranges due to the higher cost per shell.