I have tested and proven this with both perks.
If you scroll over the armor is says "carry more ammo for heavy weapons" this perk works and allows you to carry 7-8 rockets and such.
BUT! There is a HIDDEN PERK!
If you click on the armor and scroll over the heavy ammo node it reads "increased amount of heavy drops"
THIS PERK ALSO WORKS!!!!
Alchemist's Raiments has BOTH heavy drops+increased capacity on it!
Both special and heavy perks serve as double perks. Increasing ammo capacity AND AMMO DROP RATE for both HEAVY AND SPECIAL depending on which node you choose.
ALCHEMISTS RAIMENT=RUIN WINGS ON STERIOIDS!
Almost never have to put my sword away anymore!
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Swords also seem to have a hidden surplus perk so you'll get even more heavy