[RPG] Does a Mundane Arrow Fired From a Magical Bow Count as a Magical Weapon Attack

I believe this is answered on the FAQ:

Weapon Bonuses: Can weapon special abilities (such as bane) or class abilities (such as a paladin's divine bond) allow you to exceed the +5 enhancement bonus limit and the +10 bonus-equivalent limitation?

For the enhancement bonus limitation, it depends on the specific effect or ability that's altering the weapon.

Bane: This allows the weapon to exceed the +5 limit, but only against the designated creature type. For example, a +5 dragon-bane longsword is normally a +5 weapon, but has a +7 enhancement bonus against dragons and deals +2d6 points of damage against dragons.

Paladin: The divine bond ability says "These [enhancement] bonuses can be added to the weapon, stacking with existing weapon bonuses to a maximum of +5." That means if a paladin has a +5 longsword, she can't use her divine bond to increate the enhancement bonus to +6 or higher (but she could use her bonuses to add abilities such as flaming to the weapon).

The +10 bonus-equivalent limitation is a hard cap for all weapons; you can't exceed that even with class abilities or other unusual abilities.

Since +10 is a hard-cap, any futher enhacements or special abilities should take no effect. In other words, there is no greater than +10, it stops at +10.

Projectile weapons with this ability bestow this power upon their ammunition.

This text is there so we don't have to use bows as melee weapons in order to benefit from that special ability. This does not mean the special ability is transfered to the arrows, but that arrows fired from that bow gain that effect.

For reference, here are three different threads at paizo's messageboards discussing this exact topic (there are no developer comments though):

• How high can I rig up the magic on Bow +Arrows?

• Magical ammunition, magical bows and special abilities

• Exceeding the +10 limit for weapons

You would calculate the resistance to each damage separately. The modifier should also have a damage type, and you would include it with the dice roll for calculating resistance.

For example, with a melee weapon like a greataxe where you apply your strength to its slashing damage you would calculate \$(1{\rm d}12 + \text{Str Mod})\div2\;\$ (rounding down) slashing damage. And then calculate \$1{\rm d}6 \div 2\$ (also rounding down) fire damage.

So your final formula would be:

$$\left\lfloor \frac{1{\rm d}12 + \text{Str Mod}}{2} \right\rfloor + \left\lfloor \frac{1{\rm d}6}{2} \right\rfloor$$

(Those lines on the sides being the floor/round down symbols.)

RAW would probably be as described in this answer. They reference:

Damage Resistance: If a creature or an object has resistance to a damage type, damage of that type is halved against it.

Damage Vulnerability: If a creature or an object has vulnerability to a damage type, damage of that type is doubled against it.

Resistance and then vulnerability are applied after all other modifiers to damage. For example, a creature has resistance to bludgeoning damage and is hit by an attack that deals 25 bludgeoning damage. The creature is also within a magical aura that reduces all damage by 5. The 25 damage is first reduced by 5 and then halved, so the creature takes 10 damage.

(D&D 5e SRD, Pg 97)