As things currently stand, ammunition gains no benefit from material type input but it is still bound by the categorization logic used in storage.
If you craft ammunition and try to store it with ammunition that you find, they will not stack together, nor will they load concurrently from inventory if both are present. This takes up a "box" of inventory at a minimum.
One possible answer for this would be to make it possible to craft ammunition with materials similar to how we can now craft gear with any material and fix the current POI loot that doesn't have these traits (and doesn't play well with crafted). The other direction is to fully flatten all ammunition and make it default to a forced set of characteristics so that it stacks neatly and without conflict.
For me, the additional possible choices and player creativity of full crafting seems more interesting and to leave doors open to future content much more broadly but either answer is better than how things are now.
Makes sense and I'd assume it's something they were already planning to do. I believe those bullets you find have unique stats of extra crit right?
I made bullets out of pursuit btw, I'd expect extra dmg with those lol