Fictional Firearm: HC-SG15K [Eva] SMG

Note: I can't quite see some things, so if I've made any incorrect assumptions, please do point them out.

Firstly, this is a very big bugbear I have with just about every weapon design that doesn't do it: Your safety switch goes the wrong way. If the safety, when flicked down, makes the gun shoot more, that's a bad thing, since it's easy to accidentally move your thumb down (on a pistol grip) and, if you're inexperienced, pull the trigger and shoot yourself, your buddy, etc. Your safety should move the other way -- safe is the furthest down you can pull the switch, and rapid-fire is the furthest up.

Now that your gun is a little safer to use, let's talk about your magazine: It's pretty, but horrible. See, in a storm of any kind, where there's anything small or watery flying around, having an opening for all the bullets to get dirty through is an easy way to have your gun jam on you mid-battle. Say that there's plexiglass covering the hole and you still have the ability to look in and see how many bullets you have left without the risk of the gun jamming.

That little thing at the left end of the bottom rail makes it impossible to put anything on, since on a Picatinny you slide things on from one end or the other, but you can't bolt something on in the middle.

That holographic sight, while beautiful, is entirely pointless. It's much better to use iron sights -- they're easier to get in great alignment, and while you won't, on an SMG, often need the better accuracy iron sights provide, it's extremely useful when you do. Plus, iron sights don't require batteries. If you want to go on night missions with them, it's as simple as putting a little phosphorescent paint, or even buying sights that have it pre-applied if you're especially lazy.

It looks like the stock can't be adjusted at all, which is a pretty big problem -- as a bigger guy, the little teeny thing you make for smaller people won't fit me as well. Ideally, it'd be telescoping, but really any method works.

You should put some fluting on the top of the end of the barrel, tilted back. It helps fight the recoil without wasting any energy -- the bullet is already out of the barrel by the time the hot gasses get flung straight up, so all you're doing is removing some of the gas that might push it off-course.

Anyway, aside from all that, I adore your art style -- it's beautifully made. The shading is also quite nice, and the drop shadow is a nice touch. It feels cartoony with the black outlines on everything, but that's not a problem for me.

Finally, to end this, I want to compliment you on your choice of caliber: 9x19mm is a fun round to shoot, with not much recoil in a well-made gun and good effectiveness at good range.