The diamond gun skin is one of the most sought after weapon skins in Call of Duty Black Ops 4. Not only does it look cool, but it does take some skill to get it. To get the diamond gun skin, you’re not only going to have to complete all the challenges for the weapon you want the diamond skin for, but you’re also gonna need to do the challenges for every weapon in that class and have unlocked gold skins for all of them.
Head here for the challenges to unlock gold skins for each weapon.
To unlock diamond skins just start doing the challenges for each weapon in any of the different classes for primary and secondary weapons. If you want the diamond skin for the ICR-7, for example, you will need to complete all of the challenges to unlock gold skins for every gun in the Assault Rifle class. So you’d also have completed the challenges for the Rampart 17, KN-57, VAPR-XKG, and Maddox RFB.
A big part of these gun challenges in unlocking gold skins are about getting headshots. Playing in the right modes and using the right attachments can help you rack up these headshots quickly. Trying playing modes like Domination and using perks like the laser sight for better accuracy.