Can I use guns in my game?

I am making a game that has 2 to 3 guns at max. I wanted to add a MP5. My question is that, if I change the geometry of the gun a little bit, and change its name to something like A-2KR etc, and if I also changed the textures and made them look pixelated, would I still need to purchase license from the manufacturer and ask for permission to implement it? Would I be allowed to use it? Any help would be appreciated. I have read many articles about this topic, and couldn’t land on conclusion.

I myself am not too knowledgeable on this topic and could be wrong so don’t make big decisions based on this. If you are referring to the unity asset store, you can use majority of the assets, even the free ones, in any game you want, personal or commercial, without modifying it. I am also fairly sure that you can modify the assets on the unity asset store to use in your games.

However, you CANNOT redistribute the assets in the asset store (sell them, put them on the asset store, etc) no matter how much you modify them.

Most places that provide assets for purchase have a users agreement page, so I recommend reading them just to be sure.