just a guess here, but the upper edge of the arch should be a little wider in the UV layout. Grab the UV's on the upper edge and scale outwards in the x slowly, watching viewport results, and see if that helps. could also grab them and use optimize tool, then realign vertically.
Just fyi - there is no such thing as n-gons. In your image on the right, your modeling application has simply decided to not draw edges for faces that are co-linear (share the same flat 3d plane). Those are all triangles, everything always is, they are just hiding the triangle edges.
the car was just test bakes in modo to test texture resolution. there wasn't proper smoothing groups, alot of it was hard edged thus seams. I'm importing over to Maya and doing soft/hard edges there and then baking in XN. The final car will hopefully be the quality of the wheel bake.
it looks like your lightmap is bleeding black pixels. try to make sure the very edges of your lightmap unwrap fill up the whole UV to the very edge. if it isnt then unreal creates black pixels around the uv island what will bleed onto the lightmap
Ah yeah that detail is soooo super small. While we're talking about viewing distance, your edges are really hard for something that small, you should have nice soft edges, otherwise you'll need a very high res texture to hold that detail.
Went back and started with the high poly comments. Adjusted quite a bit of the mesh and got rid of all the super sharp edges. Now they are small rounded edges. Found some more reference and adjusted the overall shape and added some details. As always, feedback is appreciated.
Your rifle, you need to work on the smaller details. Lots of places where you would expect to see hard edges and not seeing them. Off the top of my head the from of the silencer (I assume that's a silencer but not sure), outer edge of the front of the scope, etc...
You can spin just an edge - doesn't have to be a pair of polys. Just select the edge you want to spin and run the same command. It shouldn't mess with the UVs unless it's a border. I've got it bound to v... but I can't remember if that's standard any more.
This is the old method of doing it, pre-4R7. You can use the crease by angle for general creasing, and use Zmodeler edge creasing to fine tune it. Those 'funky lines' are the polygon facets. Turning off smooth will harden edges on all polygons when you subdivide.
He's getting the exact same thing. The texture is infinitly stretched because, in the unwrap, the new edges you created with the inset are at the exact same place as the old edges. Your texture is applied everywehre : infinite stretch on black and white = grey. So just fookin unwrap it.