"As a DM I usually allow Luck points to be spent for ammo rather than rolling the chart if it's for their key weapons."
using luck for specific ammo types is literally in the core rulebook. using luck on your loot is a big part of the game y'all gotta start reading the goddamn rules
what's funny is that the specific ammo thing is such a core rule its bucket has its own name: luck of the draw






