Why do you want to recycle the shell casings from combat machine guns?

Recycling is actually the smallest factor.

At first, the fighter plane with machine gun as its main weapon simply didn't consider the recovery of shell casings, but directly designed a bullet throwing window and threw it out, which of course caused many casualties on the ground or accidents that affected other aircraft.

In fact, the third and fourth generation machines and machine guns are rarely used now, basically only when the two sides enter a dogfight, but how many times have you seen this situation in the past ten years? Air-to-air missiles have basically solved the problem, so the current machine gun design is very small. It is extremely uneconomical to design a projectile window for hundreds or even dozens of shells. It is more convenient to recycle directly after use, which is an important reason for recycling shells.

Another major factor in the recovery of artillery shells is that they will hit the plane when thrown out. With the exquisiteness of the fourth-generation machine, it is not cost-effective to hit an accident.