The Volatile Flow and Overload Round artifact mods are having issues with certain weapons, so I have attached a video that showcases a variety of weapons so y'all can try to identify the issue.
Weapon 1: Unforgiven. Volatile and Overload proc, as expected.
Weapon 2: Gnawing Hunger. Only Overload procs.
Weapon 3: Hero's Burden. Neither mod procs.
Weapon 4: Snorri FR5 (a gun that won't be effected by the Overload artifact mod). Volatile procs.
There isn't a clear "this will or won't work under a certain condition" pattern, it seems to be a "some work, some don't" sort of thing.
Good luck with the fix,
Hexbug