See this even possibly for armstech? Only things i've RE and managed to get a higher version of it have been barrels but anytime i do guns i get nothing. Either i am EXTREMELY unluck with RE'ing the rifles or they don't do anything at low tiers.
Apparently, from what occured earlier with someone in my party with the same problem is its tied to part of your class quest. Not in that your class quest leads you there, but for w/e reason it unlocks it.