This has been bugging me for weeks now, heavy Synth activates but gives no ammo. Happens in patrol, both raids at both difficulties, story missions and strikes. Not sure if it's a pattern but whenever I have an exotic heavy, it seems to trigger the problem. Anytime I've had a legendary in that slot, it works fine. For example, I be soloing nightfall last night. Had my Admonisher Arc ready, gave it some Synth, took out some wizards, good to go. I get to Afro-goth, switch to gally to clear some trash and go to use a Synth - no ammo! Was way over the cooldown as well. This may be an old issue but, I've never posted about it before just wondered if other guardians have had trouble with this.