I have fired the M16 (in several variants) quite a bit over the years. I have also used the Styer AUG on one occasion (the unit I was with at the time had an Aussie EOD Det attached for a while). I also have had the opportunity to fire the M 14 on a few occasions.
My opinion is that the 5.56mm round is garbage. Its too light and has no penetrating power. A cinder block house will stop the rounds. As for the M16, I have never really liked it. Uncomfortable to shoot, don't like the sight setup, just ugh... The Styer was kind of neat. The 4x scope on it was useful as long as it was daytime. Too small for comfortable shooting though (I like a longer full stock and am not thrilled with the pistol grip configurations.).
I will say that none of the ones I fired had any real problem with jamming. I have fired hundreds, if not thousands, of rounds through an M 16 and have very occasionally had a case hang up on eject. Very easy to clear (turn the gun on its side rack once with the T handle while observing the breech and you are good to go once more).
Personally, the M14 is a better battle weapon even if lugging that beast around wears on you a bit. The 7.62 NATO round has good knock down and penetrating power unlike that wimpy little hot .22 cartridge. Basically, modern infantry are carrying what is essentially a slightly more powerful M 1 carbine. That gun had little stopping power also but was useful for secruity and personal protection purposes. That in my opinion is all the 5.56 cartridge is good for. For a firefight take the 7.62 round every time.
Of the Soviet stuff I have only fired the SKS. Never saw any of the military ones that were accurate enough to bother with aiming in particular. Most are horribly inaccurate and make a very large group even when properly sighted in. The SKS occasionally also jams on eject but is easily cleared. Given a choice I would not want either it or an AK given the poor accuracy.

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