Oh Right, Cripple is the one I liked.
I also like Brand, but the passive needs a Cooldown or it will technically constantly renew itself until removed vial another effect.
Also with Experimental Clips, personally I would have the bonus damage be a flat amount. It's easier to balance that way between different guns and is also easier to control overall. Something like +15-+35 would be about right. I would lean toward the lower value since Bullets can crit.
Edit to add while I can: I'm just thinking about it and yeah, it should be a static amount. There are heroes with very small clip sizes as it is who could use the bonus quite frequently, and it should probably also only trigger on automatic reload (not manual) aka when your ammo reaches 0. Otherwise Abrams will just shoot once and reload all the time to abuse it. Other heroes that would use it a lot are ones who already have small mags or otherwise don't actually care about mag size, like Calico and Vyper. Not to mention Vyper's Reload time would go down to the impossibly short .8s. (seriously, you would barely even notice that she's reloading. Not that I'm complaining, it would be a fun way to play her.)