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?
Best Answer
To "deliver the spell through a ranged weapon attack", you have to actually make a ranged weapon attack. Making a ranged weapon attack expends ammunition appropriate to the weapon in use. You also get any other effects of the weapon attack, most notably the weapon's basic damage. The spell's effect is an add-on to that weapon attack, not a replacement.