Your sights aren't working too well because the gun model is too low. You shall raise the whole model sights will be at the height of Steve's eyes (maybe a little higher). If you want to move your whole model up just click on one part, then go to "edit" tab and click "Select all parts". When you'll be done with that you have to click "Type Specific Settings" and set the third person offset, specifically the Y-axis. Just remember to don't set it to higher values like -50 or -20. I recommend -2 and -3, these always work for my stuff. When you will be about to export your model, scroll down to the one of the latest lines of code and change from "Offste" to "Offest", if you won't do this your build will crash.
Yes yes... I guess I can give you early access to my pack... But I don't think you should download my pack yet. 1st, it's not survival friendly. 2nd, it's lacking some icons, wheels are not spinning and steering wheels are derpy and there is A LOT OF MISTAKES. 3rd, you will make your game crash at least once. By destroying a car or doing something. 4th, You need Flan's WW2 pack and probably parts package (If the engine sound isn't from Flan's basemod) I don't claim the sounds or ammo to be mine, so that's the reason why I didn't move them into my content pack. 5th, there are some models that are NOT supposed to be there. (Horse Carriage for example, and old models) 6th, Aims are NOT complete yet! I have fixed some, but not every of them.
If that doesn't change your mind about downloading my pack, or you are extremely interested in checking my progress, you can feel free to download my package.