All: "Oh."
Frederic: "Yeeeah, let's not do that then. How's your bullet former, Gram?"
Leon: "This mist charger works well. Very well with water spells."

You form another bullet, putting you at about half mana capacity, then throw it at the ground. It breaks and bursts with a flash like the first one.
Frederic: "Not better than your regular? It bursts into magic, I'd call that a fair bit better. Though, if it shatters on contact, I guess it won't have much penetration power. Hm, I guess it is a tradeoff after all."

You form another, and pass it to Leon.
Leon: "Uhhh, charge it? Like... with fire mana, or stick a fire spell on it?"

You'd almost forgotten about it since it doesn't matter much for your specific magic. Mana can have different, polarities for lack of a better word. Inclinations towards specific actions against the physical world. Fire mana would have increased effect being used for a fire spell, while ice mana would produce weaker results. For healing magic, you just use neutral atmospheric mana and don't have to worry about polarity.

Normal atmospheric mana is pretty neutrally charged, and can be used for just about anything without issue. There are polarities for each of the eight elements, specifically because of the eight elemental lords. The great sky-wide mana networks maintained by the lords each circulate with mana colored towards their individual element, and are the primary sources for elementally charged mana. You're not sure if they marshal up polarized mana and distribute it, or take normal mana and polarize it, but either way the networks are where elemental mana resides.
On its own without any spell or will to convert it to a physical action, polarized mana won't do much, same as regular mana. Though, your bullets are just spell-less condensed mana and they burst into magic on impact.

Leon: "Alright. Let's see."
He seems to form a fireball spell without activating it, same as you did with your healing spell, and attach to the bullet. He gives it a quick look over, then nods in satisfaction. You then hand him the former, and he closes his eyes to concentrate for a moment.
Leon: "There. Ok, now what?"
You take the former back and pop the mold open. There's the familiar mana bullet there, but this time instead of sky blue, it's a red bordering on orange. Sure does look fire-y.
Leon: "So that thing eats your mana to make bullets? How many can you make?"

Leon: "Mm. Alright, Karina get behind me okay?"
Karina: "Okay!"

She steps out of the way and peeks around to watch him. Leon winds back his arm with the red mana bullet in hand, and wings it at the wall. It hits with a clack, then drops to the ground.

Nothing happens.
Frederic: "Gram weren't those exploding when you threw them before?"

Leon throws the other bullet, with similar results. Hits the wall, falls down, no burst.

Frederic: "Weren't they also breaking when you threw them Gram."
You notice Leon hunch his shoulders a bit.

Nothing keeps happening, to either bullet.

You approach cautiously, and crouch down to examine the bullets. Yeah... yeah, still whole. You pick the two back up and turn around, catching a glimpse of Leon red faced and facing away from Karina, while Karina grins and prods him in the side.
Stepping back to a safe range, you wind up and throw the red mana bullet. It cracks against the wall and you see it break this time. A moment later, a small cloud of flame bursts from thin air.
Frederic: "Yup, that was definitely more fire-y."

You then let the air clear a bit, and throw the bullet with the spell attached. It impacts the wall, and instantly bursts into an impressive fireball. Definitely larger than the burst from the red bullet.

Leon: "Hmph. Now that's proper magic."
Karina: "How big would it be if you put that fireball on a red bullet and hit it inside the mist?"