Symmetry Plane Reset

Hi,
im new to Nvil and have a question about symmetry plane. I created a "tube from the edge" then used it as gun barrel.
After a while i noticed if i try to use "Symmetry Remove - PositiveWeld/NoWeld)" it dosnt work on the right place. This is how it looks like now(see screenshot).

How i get symmetry plane to center of the object? I can move symmetry plane by using "Object/Mesh Pivot" Streamline but its then not exact in the middle of the barrel. Thanks

1. Enable snapping, set snapping target to edge.
2. Activate  "Object/Mesh Pivot" Streamline tool.
3. Move cursor over an edge which lies in the center plane of the object then click LMB.

Hi , thanks a lot for help.

I tried this and it works but on the new mesh i created (screen 1,2). On the old mesh(barrel) it doesn't work , it seems that symmetry plane has offset to the pivot point, i can move and snap pivot but he is on the other position than symmetry plane. Or i understood something wrong?

Edit > Customize > Tools > Common Modeling Shortcut Tools > Align Mesh Pivot To Object Base.

An object has a hierarchy structure and may contain more than one meshes. The symmetry plane is at the pivot of each mesh.

Ahh ok that was it. Thanks!!!