You hand the former back to Leon, and he concentrates again.
Leon: "Yeah, definitely. Have to be careful with the uh, bullets. Make sure they don't explode inside the gun.

Here. This has a spell attached."
He hands you another red bullet, and you confirm that it does have a fireball spell attached.

You pull back your arm to throw, and-
Frederic: "Wai-wai-wait. Throw it that way."
You were going to throw it at the nearby wall in the narrower direction, but Frederic points down the long way of the training field, far away from anyone. You nod, then turn and fire the bullet down the far way. It starts dropping by the time it hits the wall, but still has enough momentum to crack against the wall.
Immediately, the bullet bursts into a fierce fireball, billowing out and upwards, significantly larger than either of the two previous bullets. Even from the other end of the field, you feel the heat of the flames before the dissipate.
A couple cheers come from the adjacent training field.

Frederic: "Wow. That's pretty impressive for a bullet."
Leon: "Those bullets are packed with more mana than you'd normally use for that fireball spell. Normally it'd be stupid and unstable to put that much into a fireball, could blow up in your face. But it looks like the mana only gets charged into the spell when the bullet breaks, so it's fine."

Frederic: "Heh, very carefully."
Karina: "Maybe you could coat them with something so they don't break?"

Frederic: "Well there's that other island around Madosa, the one with the earth and water sprites. Not great money, but a good first experience with magic-based monsters."
Leon: "The guild probably has some requests for materials gathering, but we'd have to travel a ways for most of that. The islands are kind of plain in terms of resources and threats here in the center of the sky."
Karina: "I bet there's jobs back in Belus for adventurers. We could go home to the capital, stock up and find some work there. And papa would let us stay for a bit if there's nothing to do."

Leon: "Hm. I bet I could get something out of the professors at the Wizard academy, but uh, I'm kinda playing hookie from there right now. So, that's out."
Frederic: "Karina's idea isn't bad. It's planting season down in Melgard, that brings out all the unpleasant little beasts and monsters that need to be beaten back. We could almost certainly find work to clear out kobold dens or something if we go to some smaller towns away from the capital."

Leon: "I'm good with that.
Er. It just occurred to me, how did you two get up here from Belus?"
Frederic: "Tagged along on our ship with some armed merchants heading north. I swatted some grumpy birds and helped with some heavy lifting, and they made sure we were safe.
We should look for something like that again if we want to go south again. What kind of preparations did you need, Gram?"

Frederic: "Right. There're stores down there of course, and an adventurer's guild presence, but if you're gonna stock up then there's no better place than Madosa, is there?
I should go ask around for southbound travelers if that's our plan, you never know when a convoy will ship out. If there's one available, anyone object to leaving today?"

Frederic: "Got it, tomorrow at the earliest."

The adventurer's academy probably has the best magic-focused library around here. Frederic and Karina take off for the docks, and as you make to head over to the academy, Leon stops you.
Leon: "Hey, Gram, were you going to go stock up on ammo now? Like special magic ammo?"

Leon: "Oh, ok. Mind if I tag along then? I do have some formal education in magic. I'm interested in those magic bullets too, it's an interesting concept."