Well...you are missing out on a good bit to be honest.
You will most likely have a pinned stock and/or a bullet button that makes it much more difficult and time consuming to change magazines.
Thankfully, you aren't limited to just 10 round magazines, too...
Now, the good thing is that you *should* be able to remove the bullet button and replace it with a normal magazine release. And if you want to possibly replace a stock if it has been pinned in place (I am not 100% sure though).