Inverted normals baking on part of mesh

[Insane_E1ite]

So I am trying to use substance painter to bake all of the maps for an M1 Garand I am building. One problem I have been running into is that the normals on the barrel are inconsistant with the rest of the mesh and almost seem inverted to me. I get two highlights (one on the main body and one on the barrel) and whenever I rotate the environment, they move in opposite directions. One thing that I think might be causing this is the fact that the barrel is hollow and the geo is very thin there. Here is a link to another forum with images

https://forum.allegorithmic.com/index.php?topic=9000.new#new

Is this a common issue and does anybody have a solution to offer?

I also know I have smaller baking errors in other parts of the model and any help with those would be appreciated as well. Thanks in advance for your help!

[僕の名前 (仮)]

Looks like smoothing groups problem.

[Pte Jack]

Go back to your 3d editor and check the face normal rotation, if using Blender and the normals are facing inward, select the the mesh and use CTRL+N to recalculate the normals, if the remain pointed inward, reverse the normals and re-export the model. Also, if you use Blender, make sure Auto Smoothing is checked OFF (no check mark)