Politics and institutional inertia will often overwhelm engineering. The USAF has a strong memory of deploying the F-4 Phantom to Vietnam without a gun. They be

Politics and institutional inertia will often overwhelm engineering. The USAF has a strong memory of deploying the F-4 Phantom to Vietnam without a gun. They believed that the Sparrow (AIM-7) and Sidewinder (AIM-9) were mature enough to win most encounters. Turned out not to be the case, and gun pods were quickly designed and shipped out. These aren't optimal since they induce a significant amount of drag, as well as taking up an external mountpoint. So since then, the idea has stuck around that a fighter must ship with a gun. The F-35A models have internal guns, while the B (STOVL variant) and C (Naval variant) can use an external gun pod. This is a tough engineering task since the pod needs to be stealthy. The value of the gun on all three variants is really limited IMHO. The F-35A only carries 182 rounds, and the B/C gunpod 220. That's just not much ammo for CAS, nor even A2A engagements.