Gentlemen, these rifles are hard to find with the 516 impossible at the moment... at least in black which I really prefer. I have come across, NIB, a 556 classic, a 556 swat and a 556 with the longer quad rail (looks very much like the swat, just a longer rail). The classic and the longer rail models weigh in at 8.2 lbs, heavier than I thought but only about 1/2 lb heavier than the 556 swat and 516 models. These certainly aren't light rifles but then my 7mm Rem. mag isn't light either which isn't a bad thing when you're actually shooting it.
Magazines are just as scarce. I jumped the gun (pun intended) and did find and buy 5 magpul 30 rounders (the newer "M" ones, no window) for ARs but I'd like to have a couple of the shorter 20 rounders or 10 for that matter, just for use at the range.