I think the concept of fast reloading is a mute point, unless you have become quite familiar with reloading your weapon under stressfull, i.e. combat conditions, it is a very clumsy hand shakeing - trying too fast afair.
I can reload any of my weapons quickly enough at the range or while hunting or showing off, etc. I would wager money that I can reload a Mauser faster than you can reload your AR or AK, but it comes though constant experience in semi-stressful conditions.
In my limited experience, I found that reloading a weapon quickly when there are bullets flying by you quite closely to be an almost imposible feat. I am not afraid to admit I was scared shitless the first few times, just plain scared the next few, but reloading under those conditions is not as easy as you might think. When you are trying just as hard to not piss your pants when a bullet hits the log you are hideing behind, man, it ain't easy.
I am sure that once you become experienced under these conditions after spending far more time in them than I was it becomes second nature, but by then, you will have developed such skill in the use of your weapon, it again becoms a mute point.