Quicksilver and Mercurial Magnum do not reload Abrams gun if he uses an ability while in the reloading animation. You need to make sure that you are not reloading before using your imbued ability. This has been bugged this way for a very long time now, not sure why it hasn't been fixed yet even when reported awhile ago.
Really frustrating bug that has existed for a very long time now. Quicksilver Reload is an item that is supposed to fully reload your guns ammo when activating an imbued ability, which for Abrams DOES work, ONLY if he activates an ability while not in the middle of his reloading animation. So if Abrams wants to use this item, he needs to ensure that he only uses his ability while he's not reloading, which is obviously a bug and extremely frustrating.