This question is based on a fallacy, that "science" makes things. A certain amount of willful ignorance is required to ask this. Firearms and ammunition are made and used by human beings, sometimes with evil intent. They were made using collected knowledge, that has been accumulated over a long period of time. When the first firearms were made by people there was no general conception of the scientific method. That did not appear until the enlightenment, well after firearms were invented. The processes by which firearms worked were later derived and understood by application of the scientific method.