Weapon Specializations in Battlefield V are unique perks that you can purchase for your weapons as you rank them up. They can do many things from giving you more powerful bullets, to giving you better aim or weapon handling, to faster reload times and less recoil.
Weapon Specializations are found in your Company Page under your class. Select any gun that you have equipped and you can change the weapon Specializations.
Each Specialization is going to cost you points to equip and every time you level up your weapon you will get the option to pick one or the other feature. Once you pick a specialization you are stuck with it until you get that weapon to Rank 4 at which point you can reset it.
Once you get to Level 4 with that weapon you can choose to change the Specializations by resetting them. Doing a reset to change specializations will allow you to make different selections but you won’t have to spend any additional coins to do so.
These specializations only apply to this specific weapon but they do apply to both the Axis and Allied factions.