From Destiny 2 Wiki
|Source||Flawless Trials of Osiris; Grandmaster Nightfall strikes|
Adept Stability is a Weapon Mod.
This mod can be found in the Flawless chest in the Trials of Osiris Lighthouse.
It can also be obtained by completing Nightfall: the Ordeal strikes on Grandmaster difficulty.
This mod increases weapon Stability by 10.
It cannot be applied to Trace Rifles and Swords.