Juudan Maouji no Isekai Kouryaku: Maougun nanoni Gendai Heiki wo Shoukan shite Attouteki ni Tatakattemo Ii desu ka

Military otaku Junya Takayama thought his life was over after being shot by a real gun during a paintball tournament in the United States. But he suddenly finds himself reincarnated in another world as the noble scion Raul. Now possessing a special ability that allows him to summon the firearms he loves at will, Raul is eager to begin a new life of combat training and field rations! However, when an enemy nation invades his home and kills his father, Raul's mother reveals the boy's surprising true nature. It's up to Raul and his newfound comrades to launch their counterattack—with all guns blazing!

(Source: J-Novel Club)