Looks good to me. How does it look in UE4? At least for me metals look quite bit different in Substance Painter than in UE4.
Not sure if its something you like, but some army stickers/flag could give some variation and identification to its look? The backside objects obviously use the same UVs and textures just flipped left-right
which gives a bit of copy-paste look that stand from otherwise finely detailed and textured model.