Well Done
I absolutely loved it. Every bit of it. Looking back, there are only a few things that would make this game perfect....
Having a secondary weapon was sort of useless, because you couldn't switch during a reload. This makes it only useful to have a secondary if you're testing another weapon out... I think it would be sort of cool to have all weapons available as you unlock them. Maybe numbers as hotkeys to switch? You ARE in your blockade, where you would keep them all.. so it is a realistic idea.
Also... I didn't think it was a HUGE deal, but after you get the last weapon, the game is sort of... "egh" for those last few rounds, but only because you've already beaten the game.... you need to be able to acheive more in the game than just weapons and such. Why not add secret acheivements or something? Just a little incentive to playing to the end for those that have done everything else before then.
Those are really the only things I could think of that made this game short of perfection. I think you did an absolutely amazing job on this, and I hope that you continue to create games as good as this one, and better.