"Spell storing: A spell storing weapon allows a spellcaster to store a single targeted spell of up to 3rd level in the weapon.(The weapon strikes a creature and the creature takes damage from it,the weapon can immediately cast the spell on that creature as a free action if the wielder desires. (This special ability is an exception to the general rule that casting a spell from an item takes a least as long as casting that spell normally.)... Once the spell has been cast from the weapon, a spellcaster can cast any other targeted spell of up to 3rd level into it. The weapon magically imparts to the wielder the name of the spell currently stored within it."(DMG,225)
Vapnet kastar stavningen, inte wielder. Behandla är som om wielderen använde UMD för att aktivera en trollstav eller rulla. Jag tror inte att warmage bonus skulle gälla eftersom han inte kastar stavningen, vapnet är (om en warmage skulle göra en rullning skulle bonusen inte genomföras).