All armour pieces and sets have a durability bar but it does not get affected or go down in anyway possible. If you do implement the durability of armour I would suggest:
Wooden Helmet = 100 Hit Points, Bone Helmet = 200 Hit Points, Leather Helmet = 300 Hit Points
Wooden Chestplate = 200 Hit Points, Bone Chestplate = 400 Hit Points, Leather Chestplate = 500 Hit Points
Wooden Leggings = 150 Hit Points, Bone Leggings = 300 Hit Points, Leather Leggings = 400 Hit Points
Wooden Boots = 100 Hit Points, Leather Boots = 300 Hit Points
1 Hit Point = 1 5.56 Bullet (Damage/Hit)