I don’t know if this is a glitch or not, but as soon as I equipped a saddle on this bird (tamed obviously) it turned into a flying portable smithy holding all of my smithy Engrams. Now I can craft more bullets on long hunting trips.
Getting a massive TLC update in March 2018. The saddle will act as a mobile smithy, Argentavis will be able to carry with Talons as well as with its beak, reduced carry weight on obsidian and a few other unannounced resources (similar to the mammoth and wood), and will also gain a Rapid HP Regen upon eating (likely from devouring corpses and not specifically food from inventory). Like so people can see!