If Bombardment is somehow cast while another spell is on the stack, that spell becomes a Missile. Since that spell has no target chosen for its spell ability, it won’t resolve. This is true even if that spell had a target for an ability it had.

You must keep cards that were in your hand as Bombardment resolved separate from those that enter your hand later in the turn.

The Missile characteristics are copiable values of the affected cards and spells.

If a card you own is a Missile and changes zones other than by being cast as a Missile, it stops being a Missile.

Cards you own keep any supertypes they may have, such as legendary and basic.

If any portion of your library is randomized, those cards become new objects that aren’t Missiles.