First of all, it's very important for me to keep the story as realistic as possible, though with some liberties. So an example, the main character is a cyborg, working as a sniper. She looks human in every way, but has been 'upgraded' with technology. At least one of her eyes are artificial, giving her some sort of nightwishion or thermal vision, as well as a head's-up display (HUD). This allows her to see the distance to the target, the wind direction and speed, stuff like that. Nothing that isn't possible with modern technology (like nightvision googles etc), but she has it installed in her eye(s). You get the idea. So anyway, she needs weaponry. A sniper-rifle can shoot from a long distance and is very accurate and deadly, but it's slow to reload and quite useless in close combat. For this reason, she needs a bigger weapon too. My idea was that she already has a rifle, so why not use it as an assault rifle if she has to? Instead of shooting one bullet at a time, she can flip a switch and shoot lots of them at once. This gave me a few issues: 1. The barrel. A shorter barrel will be better for the assault rifle, but makes the sniper rifle less effective. She mainly works in a city anyway, so she doesn't really need to be able to fire a really long distance. A few blocks will do. Can she use the same barrel for both firing modes, or do you think she needs to go Aliens and have a two rifles combined in one? 2. The bullets. Sniper rifles have a higher caliber than assault rifles, so what caliber do you think would be the best? Higher for the sniper and less effective assault rifle, or effective assault rifle and bad sniper rifle? Keep in mind she's modified with technology, so she (almost) always hits her target. A bullet in the head will kill you, whether it's 9 mm or .50, but she can't really take that chance. Likewise, if she has to use an assault rifle, she needs it to work as good as possible. 3. The magazine. The higher the caliber, the heavier and bigger the bullets. She needs small bullets for the assault rifle and big one for the sniper rifle, so how many can she have? Keep in mind she has an ammo belt with more magazines over her chest (from left shoulder to right waist), so she has a few spare magazines if needed. But they won't hold much ammo each and takes a few precious seconds to reload. Thanks for any input.