Just makes the Breacher not a supply hog by giving it two shots on supply instead off 1 allowing you to use it without bashing your skull in by having to hog 3/4 of a supply to fill your angry hot dog shooter.
I wish there was a mod that made the resupply a 100% ammo, grenade, and stim refill to prevent the need to double dip (the team call in version, not the supply pack)