You can improve your arcane ammunition with more powerful magic.
Prerequisite(s): Int 15, Arcane Strike, Spell Cartridges, ability to cast 4th-level arcane spells, proficient with firearms.
Benefit(s): While your gun is imbued with power from the Arcane Strike feat, you can spend a standard action to cast a spell of 3rd level or lower and deliver it via a force bullet. The spell must have a range of touch or produce a ray; if the spell would produce multiple rays, the bullet delivers the effect of only one ray. If the force bullet strikes a target, it deals its force damage and also delivers the effects of the spell. If the force bullet critically hits a target, the spell deals double damage.
the feat allows you to imbue touch spells into your firearm and deliver them via ranged attack, it covers what happens with rays that fire multiple rays, but it doesn't cover what happens with touch spells that grant multiple charges like chill touch, or frostbite or elemental touch. Does each subsequent attack with the firearm grant a delivery of the spell in question or is it just one casting one charge when delivered via gun?
So I guess my 2nd question is, does the standard action permit you to fire the weapon after the casting/imbuing occurs? Like when you cast a touch spell you are usually allowed a free touch attack on the same turn, or if you cast a ranged touch spell you usually fire the spell at the sametime, do either of those matter here with this particular situation? or is it cast then wait until next round to fire the gun/spell?
Well here's the next question then,
If the force bullets do count as force and magic and thus hit incorporeal creatures 100% of the time, does the spell attached also hit or does it still have to role a miss chance?