The Myrmidarch Magus archetype reads, in part:
At 4th level, a myrmidarch can use spellstrike to cast a single-target touch attack ranged spell and deliver it through a ranged weapon attack. Even if the spell can normally affect multiple targets, only a single missile, ray, or effect accompanies the attack.
At 11th level, a myrmidarch using a multiple-target spell with this ability may deliver one ray or line of effect with each attack when using a full-attack action, up to the maximum allowed by the spell (in the case of ray effects). Any effects not used in the round the spell is cast are lost.
I guess I'm having a hard time rationalizing between RAW and the theater of the mind's eye - can you make a "ranged weapon attack" without using ammunition? I guess, the question is, are you shooting your spell through your weapon, or are you putting your spell on your ammunition?