Minimum range
From MechWarrior: Living Legends Wiki
Minimum Range is a trait shared by many types of Missiles like MRMs, LRMs, ELRMs, ArrowIVs, Standard ATMs, and ERATMs. Missiles fired at a target that is closer than its minimum range, it will either miss the target or fail to detonate on impact. Players are advised to stay far enough away from their targets that their missiles are outside of their minimum range. In the case that an enemy has weapons with a minimum range, players are advised to run towards the enemy so that the enemy's weapons do not work.