The World War II was a golden era for guns, machine guns and firearms. While the premise might sound “catastrophic”, the fact of the matter that innovation in weaponry was at its best during one of the worst wars in history of mankind.
People nowadays cannot appreciate the beauty and the simplicity of the mechanism of World War II weapons, simply because weapons are advanced, and the technology is much more different.
Back in the time, the striker hit the explosive, which then ignites the gun powder that is inside the pullet, the gun powder turns into a gas, and the gas pushes the bullet out of the jacket using the built up pressure. Simple and clear way of functioning.
If you want to see an educational video, that can be safely classified as “superb lesson in physics”, check it out. The physics aspect will help you understand and get Newton, as many of his principles were actually applied to weaponry and weapons innovation.