I didn't do your homework because, regardless of how simple it is, it is still your homework. And because it was so simple, you should have posted it, at the very least, about two pages ago when you were first asked. Now...
You do realize that these gases do not just disappear in the HK system, nor does the HK system magically eliminate the need to control over 50,000 PSI, and the corresponding stress on operating components, right?
And you do realize that none of the people you are addressing are stupid, or uneducated, right?
This is a forum about guns and shooting. All of us are here because of our interest in these hobbies. As a whole, we are much better informed about firearms than the general public. So believe it or not, what you are discussing as if it is some secret that you are letting us in on for the first time is actually widely regarded as common knowledge around here. So yes, for the last time, I and the vast majority of the people you are addressing here as if we are simpletons are well aware of the differences in operation of the rifles being discussed.
If you look on Youtube, there is a video of a CETME extracting with the extractor removed. The empties are extracting, even if they aren't always ejected from the rifle. You are probably aware that the chamber of the CETME/HK roller-locks are fluted. And you probably are aware this is to aid in extraction. If you've put two and two together, you realize this is accommodated using the same hot dirty gases used to cycle the mechanisms of the gas operated rifles. So while your rifle doesn't rely on these gases to cycle the mechanism, ours don't rely on these gases to extract the case.
What you have done is list theoretical advantages of the G3 without acknowledging that in practice, all three rifles have demonstrated remarkable reliability and durability. None of these rifles are known to be finicky, unreliable, or especially fragile. This is why torture tests in general are so worthless--because most modern designs are close enough in intrinsic mechanical reliability that which is better is not really a matter of design so much as production and minute variances within individual rifles. You can nitpick all you want about unquantifiable advantages your rifle may or may not have in reliability due to the differences in its operating mechanism, but all you end up doing is pointing out the differences in your rifles design while apparently assuming that everyone agrees different is automatically better. But here is a newsflash for you--everybody probably holds a belief that the differences in their rifle's design makes it better too. This probably relates to the desire most have to believe that what makes them different makes them better than everyone else. But different does not automatically mean better. Your rifle is different. That is all.
"...nothing says 'I WILL shoot every last one of you before you have time to reconsider your poor choices in life' like an AK."