Talk:Forma/@comment-128.72.174.208-20140208130116/@comment-203.219.236.80-20140210074157

i think the chance MIGHT have gone down with the update, unless it is a 33% chance at wave 15.

Since "15 waves guarantees a Prime Part, Forma or a Key", https://forums.warframe.com/index.php?/topic/172911-prime-gear-drop-locations/

Meaning the drop at wave 15 could be a prime part, forma, or one of the void keys. So unless forma has a higher priority then its probably got closer to 15% chance. Of course it could drop at a different wave but they also have FC's, Resources (orokin cells seems common), so probably less chance during those.