Weapons can be upgraded using the correct Upgrade Points that match that Weapon Type.
These upgrades apply at the Weapon Type level and not at the Weapon Skin level, therefore once a weapon (like an AK-47) is upgraded, all skins for that Weapon Type receive the upgraded parameters
Weapon upgrades are tied to the player account and do not transfer when a weapon skin is sold
Here are some of the weapon type parameters that will increase as a weapon is upgraded:
Damage modifiers in PvE
Elemental effect modifiers in PvE
Ability to use new Special Bullet types with this weapon
Offensive power boost modifier (for Land Staking)
Defensive power boost modifier (for Land Staking)
Land control-related boosts, like Offensive and Defensive power boost modifiers don’t apply to guns that are already staked to a land plot, and have to be unstaked in order to receive the upgraded stats.