Gun moves when you play an animation when the gun is not suppose to move?

Hi I have been trying to get experience making some little fps animations in unreal engine but I have experienced a problem and this has occurred multiple times back in other projects and some how i fixed it and i dont remember how the issue is in my project I have some arms at the moment where i attach the weapon to the arms and it works perfectly it looks just like how it is in blender but when I make a fire animation for the gun skeleton and play the animation the whole gun moves forwards and stays there even though i have attached it to the arm for some reason i will include two pictures of how it looks for help.