Until I bought a 556, I would agree with you Cal-gun fan. I have owned and shot many AK's, including select fire rifles, and they are really great rifles, but there are some shortcomings to the 1940s Kalashnikov design, as I see it, which have been addressed or made current, in the SIG design. And I disagree that optics mounting is easier on the AK.
The 556 shares a similar operating system with the AK, but the remainder of the rifle is actually different enough to warrant discussion on whether the differences are improvements or not. To my way of seeing it, the trigger mechanisms on both the automatic as well as the self loading 556 rifles seem to me unnecessarily complicated, and closely resemble the HK roller lockers or the FAL. The disconnector is sort of on an eccentric sharing the same shaft as the trigger, and I think I prefer the Kalashnikov system as it is simpler to my view. MTK borrowed extensively from Mr. Garand's trigger system, and it is a good design to copy.
The magazine release is pretty much the same on the Kalashnikov as it is on the SIG.
The split receiver a la M16 is superior to my way of seeing things, as one can clean the rifle from the breach, rather than from the muzzle. The AK is a front stuffer as far as cleaning rods go. While I haven't come to a definitive conclusion on the gas tubes, the methods of mounting up the gas tube on the AK is nearly an interference fit, and it is my belief that the SIG gas tube being semi floated would in theory at least tend to allow the barrel fewer static forces to affect the harmonics, and thus render it more accurate, all other things being equal.
The SIG handguards are longer and seem to control heat a lot better than does that of the AK. If you don't grip the AK just right after a couple of magazines, it will scorch you. If you are using the old wood handguards on the AK, I have on more than one occasion smelled them burning or smoking in rapid fire situations.
The SIG sight is more conducive to an accurate iron sight setup due to a longer sight radius, and while the folks in Exeter have deigned to not share the excellent rotary diopter that comes on the 556 Classic with the 556R, these sights are an improvement in my view over those of the AK. Longer sight radius, rotary diopter with CQB "notch" a la HK roller locker, and what's not to like? Good setup. --One of the features of the SIG rotary sight is that it will not allow one to rotate from CQB notch to 300 meter aperture. I can understand the philosophy of requiring the rifleman to ratchet thru 100, and 200, to arrive at 300, but I'm not so sure it is always a good idea.
Integral pic rail on the SIG receiver facilitates the installation of good US or "western" optics while not requiring the rifleman to raise his head off the stock for a "chin weld" as one must on the side rail AK mounted optics. This favors the SIG.
In all the Kalashnikov is an excellent weapon, and I like it a lot. But I do think that the SIG package is a "product improved" AK, at least as far as are the ones that I as a lowly Prole can buy here in the US.
This is my view.
