Easier M16 hint:
Instead of jumping into the foxhole, lie down next to it as close as possible on its left side. The game will allow you to qualify in the prone rather then the standing position.
Shoot your currently selected weapon. The bottom left of the HUD shows you how many bullets are in your current magazine and how many reserve magazines you carry. Fire the weapon until just one bullet remains in the magazine. Glance at how many magazines are left. After doing that, reload and your magazine count will not change, but your bullets will be refilled.
Use M203 with scope:
When you are able to modify your M4, go to your Personnel Jacket. Select the scope you want to use. Then, select the M203. When it tells you that you cannot use the M203 with the scope, turn off the Xbox. When you turn it back on and go to your Personnel Jacket, you will have your M4 equipped with a scope and a M203. Note: When this glitch is activated, you will not be able to use the iron sights correctly. You can only use the 4x zoom.