Fr Dave's Magic Missile

FrDave had this very fun interpretation of Magic Missile a while back. Here's a formal write-up of it that spells out what he interpreted, with some tweaking of my own.

Magic Missile
Level 1 Spell
Duration: Until Fired
Range: 15 meter increments as a ranged weapon

The caster creates a magical missile that conforms to the player's design, as well as a quiver to hold up to 20 of these missiles. When the caster fires a missile, whatever means to fire the missile is needed magically appears, disappearing when no longer needed. The missile is +1 to hit and does 1d6+1 damage.  The caster may fire as many missiles per round as the caster's level divided by three, rounded up (level 1-3: one missile/round, level 4-6: two missiles/round, level 7-9, three missiles/round, etc.) and may have as many quivers as the caster's level divided by three, rounded up (as many quivers as the number of missiles  a caster can fire in a combat round.)

In my game, ranged weapons all have a rate of fire between one and three times per round. An interesting observation is that this spell allows magic-users of 10th level and higher to fire their missiles at a rate higher than any mundane archer or other practitioner of ranged fighting.