Ok so this has been said a few times, hopefully with enough repetition it will be addressed and fixed...
When you have an item on that grants you the ability to carry more Heavy ammo it results in the loss of ammo when you die and go to orbit
Edit: also noticed the increased heavy ammo perk does nothing if you have field scout on your heavy weapon
-
The game is DESIGNED to take heavy ammo away from you when you go to orbit. The dying part sounds like a glitch if you are talking about PVE. In PVP, you lose you heavy, not matter what perk your armor has, when you die.