Thanks Mike.
The .50 cal expended cases and links were definitely ejected from the P-38 through the 4 chutes in the nose. The 20mm cases were a lot bigger than the .50 cal cases, and if ejected, would have been closer to the props. They could possibly have done a lot of damage to the fuselage pod. I suspect that is why they were retained in the nose and emptied when the aircraft was on the ground.
Ron