Right since I can't sleep taking a look at this now.
First of all your UVs are still not setup properly for 2:1 UVs, they need to take up the entire UV square otherwise basically you're saying 1/2 of the texture isn't being used:
Should look like this:
When then when you apply a 2:1 texture to it, looks like this:
For example, if you look at the Mirages Textures (first 2:1 texture I can think of, not a very good example but best I have to hand), you will see its 2:1 texture looks like so:
And if you look at its (really bad) UVs you can see it looks like so without the texture applied:
But when we apply its texture then the UVs become un-squished and make sense:
You really need to make this change as per my last post before you do any more baking, even if they are just baking tests since any you do will be useless or pretty meaningless as the UVs will change.
Moving on, while I know packing the scope UVs into that little space left was a hard challenge and some bits were inevitably going to be smaller rez than the main parts of the model, some bits are just too low rez right now and I think you can do better looking at it in 3D. Mainly looking at the open scope cap, scope front and other bits that are right in front of the player you can see a much lower rez than even the main tube of the weapon which is further away and not square in front of the player like these bits, and they really need to be scaled up.
First of all you can make some savings by overlapping some common bits. For starters, both scope caps right now have unique textures where they could easily use the same texture, especially since you are only really going to see the inside of the rear cap, and the backside of the front cap, meaning you can get away with the other two using each others textures.
Also speaking of these caps, do you have any refs with them? I'm failing to see any refs with them and I think it may be worth removing them, not only to save tris and UV space, but also because they are going to look odd ingame unless animated really well.
Next as I mentioned before, the inside of the scope just needs to be a flat black and you can scale this down to use just 1px of texture even, since if you look side on at a scope, you will not see any detail inside, all you will see is the reflection on the glass until you start looking straight down to the other end where you will then see right though, with the zoom too:
Speaking of which, you also need to model the glass for the lens on the front side of the scope, just the front side, don't bother with the back side or with modelling glass for the far side of the scope either, and it doesn't need to be UVed to the main sheet either, will use a common scope glass texture and an ENVmap reflection texture on it too, but you do need to model it in
Next the back side of this bit doesn't need to be as high rez as the rest as it is unlikely to be seen at all, even with the caps removed since the iron sights are blocking its view and its facing away from the players view. Although I would re-UV the edges to be stitched to the sides so just the inner most face is detached and scaled down:
Anyways main areas I would focus on increasing their UV scale would be these bits which are either right in front of the player, or currently just too low rez, or both and if you remove those scope caps, make the inside of the scope takes up only a tiny, tiny bit of UV space somewhere out of the way and the other things I mentioned I don't think you will have an issue and can possibly scale up other bits too
Oh and one other thing, you need to also fix up your smoothing before doing an AO bake as otherwise, you will get hard shadows on each face which will only enforse the blockyness of the model, even after its been smoothed instead of the other way around:
I've tested, it exports well .bundlemesh and .baf.
