Is Moon Knight only using guns in the Vengance of the Moon Knight series, or is he using them in the mainstream comic as well. I only read like the first 10 comics of the 2006 reboot and he doesn't use guns, which kinda disappoints me.

The Vengeance of the Moon Knight is the current ongoing MK "mainstream" comic. That and the new Secret Avengers are the only two titles that Moon Knight is in (excluding special events like Shadowland).

MK doesn't even use guns in Vengeance of Moon Knight (I believe). He uses entirely non-fatal means of combating his opponents, so he uses darts and grappling lines and whatnot since he's trying to reform his image. When he was fighting against Deadpool he refused to really go at him because he thought he'd kill DP, but when he found out that he has a healing factor he chopped him up real good.
 
So, yeah, sorry to disappoint you but when he's MK anytime recently I don't think he uses guns at all.

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He's ex-military, a former mercenary, and has no problem killing criminals to "satisfy" Khonshu. In his hangar are all kinds of weaponry, and the Mooncopter is equipped with all kinds of lethal weaponry. That said, Marc will more often than not prefer the up-close-and-personal style of fighting, particularly in Charlie Huston's reboot issues. I've read nearly all of Huston's novels, and although a lot of his characters use guns, most of the crazy ones will resort to beating/stabbing their victims to death. And since he wanted to portray Marc as psychotic.... well, you know.  "