Pics or it didn't happen:
The idea of balancing around inventory space is something I've had for a while, and I went with a flechette rifle because all good scifi should have one. They tend to work terrible in real life, but it's fun to dream, right? "Flechette" refers to long thin needles, and usually lots of them. They work very well under water. Some of my favorite scifi that has featured them is Bungie's Marathon Infinity and Neal Stephenson's Snow Crash.
http://en.wikipedia.org/wiki/Flechette
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Version 0.0.1: Here's a link to the previous version.
License is CC BY-NC 4.0
TODO