To find academic papers concerning firearm and powder development, you will probably need to find a university that offers a degree (and probably an advanced degree) in that subject matter. Considering how relatively few firearm manufacturers there are around and the fact that there really aren't that many new firearm models produced each year, I doubt that there would be many universities that offer such degrees. I suspect that most firearm designers start off with degrees in mechanical engineering and anyone designing powders probably starts off with a degree in chemical engineering. From there, I suspect that they get more experience while working at various companies, none of which would result in research papers being generated.