The Sorcerous Blade Channeling feat says:
When you use any ranged sorcerer attack power through a dagger, you can use the power as a melee attack. If you do so, the power’s range equals your melee reach.
Does the player get the dagger's +3 proficiency bonus? I would prefer an official reference if possible.
You apply the weapon proficiency bonus only if the Sorcerer attack power has the "weapon" keyword.
From the Bonus definition on DDI:
Proficiency Bonus: Gained from proficiency with a weapon, this bonus applies to attack rolls with that weapon. An adventurer gains the proficiency bonus only when wielding the weapon and using powers that have the weapon keyword.
Looks like there are currently 8 Sorcerer powers that have the weapon keyword, all in Dragon 379 and 390. Most are already Melee weapon attacks so they would not benefit overmuch from the Sorcerous Blade Channeling feat.
You should, since melee attacks have the "weapon" keyword, and you would have the dagger to use already as an implement for your ranged attacks.
