SO um, any Good MC that use gun to as his main Weapon? Of course Male MC. Similar to Novel extra. I don't mind if there is mixed element inside the stories. As long MC use gun. I don't know why, for some reason i got feeling wanting to read Gun user novel.
Try Gun-ota ga Mahou Sekai ni Tensei Shitara, Gendai Heiki de Guntai Harem o Tsukucchaimashita!? The mc tries to make guns in a fantasy world Or Arifureta Shokugyou de Sekai Saikyou The mc uses magic guns. Its better if you skip the anime and go for the manga or novel itself
I want to recommend The Protagonists Are Murdered by Me, but I couldn't say for certain that gun is his main. Most of the time he use guns, but sometimes he also use a sword too, depending on the situation.
https://www.royalroad.com/fiction/19690/out-of-space https://www.royalroad.com/fiction/30178/fireteam-delta - I only read a couple of chapters, so I don't know if they keep their guns.
There’s a series about mc transported to another world as his gun wielding virtual game character. https://www.novelupdates.com/series/magic-bullet-in-magic-land/
The Legendary Mechanic The Record of Unusual Creatures, he's a gunfighter(Psionic gun) until he obtains space elves tech weapons