i'll make it so when you fire, you launch ammo on the ground, the same way you drop it when you die
Something about this makes this seem not-so-fluid and makes it play out more like Gcat's rather than the fast action of T+T... Make it one use and maybe have it explode ammo all around the player, I think that'd help! :)
If exploding around is bad, you could directly add ammo to the player if possible, or just make it one use.
Just to make sure, my thought was to create different variations of ammo piles that you can modify in RTB prefs to change the ammo types given; I.E: No need to make multiple bricks having all types of ammo except rockets and grenades!
But yes, a variations of these held ammos are also cool! Allow each item to have different ammo in each of them w/ RTB prefs.