History of Killing Tally

Killing Tally is a weapon trait: kills increase the weapon's damage until it is stowed or reloaded. It grants up to 3 stacks; per Blueberries the damage bonus is 10%, 20% and 30% at 1, 2 and 3 stacks. A search snippet of light.gg lists a PvP value of 5/10/15%.

Notes

The Destiny 2 Wiki and Blueberries say it was introduced in Season 17 (Destiny 2 Wiki says Season 6; the sources disagree). It is commonly found on Trace Rifles and Machine Guns. It appears on Ulterior Observation.