Season 4 is upon us, and boy, are there a lot of JAK Aftermarket parts to unlock in Modern Warfare 3. Here is how to get your hands on them all. All Jak Aftermarket Parts in MW3 Season 4 There are a total of 8 new JAK aftermarket parts to unlock for various weapons in Season 4 of Modern Warfare 3. Some only make minor changes, while others will be considered meta in no time. JAK Harbinger Kit – M4 Assault Rifle This is an obscene JAK Aftermarket part for Modern Warfare 3. It allows you to chamber the M4 for .50 cal rounds, lowering the fire rate but delivering absolute missiles. Expect recoil that will blow your shoulder out. You can unlock it by completing any 5 challenges from Week 1 of MW3 Season 4. Screenshot: PC Invasion JAK Gunslinger – Basilisk Handgun A huge boost to the rate of fire and responsiveness to trigger with a .357 ammunition attachment. You can unlock it by completing any 5 weekly challenges of MW3 Season 4. JAK Volkh – KV ...