Easily one of the best card of Tommy's pack: Custom Grip fixes so many issue with firearms (mainly the risk of running out of ammo at the wrong moment) and actually makes guns worth building around at least and gives a serious blow against melee's supremacy in Guardians deck (alongside the Machete nerf)
For one resource, you get INSANE value: a play action of a weapon, the ability to return the weapon to your hand and play it again or another one. So essentially you get to refresh a gun or replace it while keeping in hand the original gun you played. That is incredibly good tech at level 0 and it scales so, so well when you start using higher level guns, like the Lightning Gun.
This is a staple in all of my firearms deck that can access it: it singlehandely removes any risk of running out of ammo in inopportune moments.