Hello all! I am currently working on a project in UE4, and have designed several 3D models for it in blender. But when ever I import them into UE4, a side of the model is GONE, this only happens to cylinders and the stock of the weapon model that I made. It is very upsetting and it has happened always! I don’t know how to fix it either! I have tried setting the smoothing groups to normal’s or faces or edges. None of them work. Any way to stop this?
ok things to check when using blender with UE4, the size of your mesh is very important if its to small in blender then you will lose triangles when you import, make sure you apply all modifers before you export, re-calculate normals as they might be flipped, i’ll be honest to say i’ve never had that problem so i’m guessing
I have done and tried all of those solutions 
ok go to the forum and send me a pm with a link to the file and i’ll have a look at it tomorrow
I dont know if your issue has been solved yet by now but I want to ask are your normals facing the right direction? In blender if you extrude a circle in the negative direction it inverts the normals which would be invisible in unreal. Check that.
I used subdivision surface, could that be causing something similar to that you described?