>>64248864
Masamune Shirow was that.
80-90s manga. Used to watch GSG9 or SAS training tapes for inspiration for his tactical police manga: Appleseed, Dominion, Ghost in the Shell.
He wrote out his thoughts about firearms at length in companion documents to his comics and most of them were half fuddlore and half exactly from basic encyclopedias.
This is one of his least bad 'flexes' where he worked to teach his readers about different types of firearms and ammunition.

Most of his gun designs and military tech designs weren't very good, imo.
Good writer otherwise, however.