Freeze parts of an animation?

Is there a way to make the arms stop moving from the default animation? Because I am creating a FPS game and I have replaced the model with a 3rd custom model so the other players can see each other. The problem is, when I apply the AnimStarterPack, in-game from the first person perspective, the weapon moves all around when moving the character. So I would like to know if there is a way to freeze the arms so it looks better.

freezing the arms is not going to make it look better. You need specific animations.

Export the one you have, and modify the arm position to match your needs.
10 times more proper then anything else.

And “anything else” wise you could replace the top of the body with a montage, but then it also costs you perfornance on top of not being proper.

Thank you so much! I managed to do it by cutting the body in half and making it so that only the owner can see it and I made the full mesh so only the other players can see it.