Indeed Z.
One thing I would suggest which I can't quite tell if you have done or not but the inside of your barrel you should make into a cone rather than a Cylinder with a capped end since it will save many tris and look just the same
Also a piece of advice, I see you have been working on loads of stuff all at once. I strongly advise you to only work on one project at a time and dont move onto anouther project until that project is 100% done and dusted (at least in your modelling, UV, texturing etc departments) epically when it comes down to weapon modelling etc since otherwise you will find yourself with lots and lots of unfinished stuff about that's almost finished but not quite done and not ingame because since it wasn't 100% done the exporter couldn't put it ingame until it is and you will become overwhelmed with the amount of stuff you have to do.