So it uses wind magic but it still needs magazines and casings? what? Why doesnt he just make a big paintball gun that shoots a thousand metal pellets? If it works on his magic it doesnt need to look like an ak to have its firepower
Yeah. It was revealed the dude was an aviation engineer. I wonder how he even knows how an AK works, considering he's Japanese. Japan is one of the most weapon neurotic countries, so he would have needed to travel abroad to ever hold one in his hands. While an AK is not a super complicated weapon, which is why it's reliable, it's still a refined piece of engineering. You can't create a copy of one without extensive gunsmithing knowledge and experience. It's pretty strange the manga made a point of the dude being an aviation engineer so that he could create his airplane, but then creating a gun is apparently something every Japanese can do. Hilarious.
And yeah, it was pointless as well. I have no idea how the casings help his case. You can't compress air into the them, the bullet would just fly away if you tried. So, he needs to create the wind magic effect every time he pulls the trigger. But then again, in this manga everything just keeps going the MC's way with minimal effort, so nothing needs to make sense.
What was the point of learning swordsmanship if your just gonna use a gun? If he uses this all the time his swordsmanship will deteriorate.
I guess to get stronger physically. To build muscles and stamina. He got the swordsmanship coach for that. However, otherwise you can see the dude actually does act like a person from our world realistically would: extremely carefully and avoiding risks. He's using concealment as much as he can, and now he's using a gun to kill the enemies from a distance away. He's not about to lose his life in a swordfight. I guess he will just put a few bullets into the prince's legs and arms in the duel to save the villainess... That would be funny.