Mesh face not rotating at the same rate as rest of the mesh When ever I try to move a bone in pose mode, the face of the barrel of the gun doesn't move as fast as the rest of the mesh, resulting in the pictures below.






Any idea on how to fix this?



Another, earlier version of the setup:


This one is better.
Thanks for the file, I feel now I can understand what you meant.

in weight paint mode you can see that (at least) some bone have incomplete weights to that arm: some part are blue while they should have been red.



this is causing a part of the arm not moving with that bone:



You just need to correct weights (all red) to make it move better with the bone: