Just equip the 10.5” Commando Barrel and it will unlock. However, it only works with the CAR-15 and M607a handguards.

First, you need to equip the 10.5” Commando Barrel. Second, equip the M231 FPW handguard. Now, you should have the FPW fire mode unlocked.

This shares steps with the previous one. However, you first need to remove all other attachments. Then equip the commando barrel and FPW handguard. Now, you should have the patriot magazine unlocked.

All you need to do is enable Pack-A-Punch.

All you need to do is switch to semi-automatic.

Same here, switch to semi-automatic.

This can be unlocked by switching to either the A4 or CAR-15 top.

Let me know if I missed or was wrong about anything!