Spell Arrow question

[Whitewings]

Can Spell Arrow be cast on non-arrow targets, such as shuriken, sling bullets, gun bullets, cannonballs, and similar?

[ehrbar]

The spell description continues on p.66 of Magic as follows:

The GM may decide this spell can work on other kinds of missiles (e.g., bullets). If so, for those missiles, multiply the contained spell’s casting cost by 1/10 the missile’s Max range, instead of 30. If the missile should pass beyond the Max range (for example, if fired from a more powerful gun) the spell is wasted. (This last rules does not apply to actual arrows and bolts.) Note that the need for a jewel still applies to bullets!

[Whitewings]

Thank you for such a prompt reply.