3 AP to convert ammo into another type of ammo is way too expensive, in my opinion.
My suggestion is to make this cost 1 AP with Master Gunsmith and 3 AP with Gunsmith.
I understand that the features of Master of Munitions was split between Way of the Fast Hands and Gunsmith/Master Gunsmith - it however just ends up feeling horrible that it costs three times as much AP to consolidate your ammunition.