Right took me a bit longer than I thought since I did a little more than just repacking
First I added a little cylinder onto the base as it had nothing to rotate around, can always remove it with ease if the vehicle your putting it on dose have something here but best to have it as part of the RWS anyways:
I also added a few more faces behind the ammo box bit so it can rotate more than 15degs up/down than it could only before without showing a missing face, now can rotate something like 60degs up or something but w/e it is, should be enough
Next I unwelded these bits so they can fully rotate together, before the bar was welded to the sides which it didn't need to be either as there was no chance of zfighting there, saving a few tris too:
Then for your UVs, I started off by welding up a lot of them, you had pretty much nothing welded up like a low poly model UV that was going to get baked to, with the different smoothing groups all separate. Since your not doing any baking here (that I'm aware of at least) there its best to weld the sides up as not only dose it make cleaner textures, but saves quite a bit of UV space overall. Then next of course was packing which I've ended up with this. Note the massive gaps between each UV is because the final textures should be 512x512, possibly even as low as 256x256 and then taking into account mips on top of that, the big gaps are to help minimise texture bleed for these small sizes as the smaller the texture, the smaller the gaps

Although possibly a bit on the extreme side still, better to have bigger gaps than having texture bleed I find

And for the packing, you can see for yourself how I've used the space, although a few gaps most things fit into each other pretty well maximising usage while still keeping a gap between each UV
Also fixed a few small smoothing group issues here and there
Will PM you the new files shortly
