I have a SOCOM 16, and I love it. For one, it looks cool and no one else at the range has one. It is super loud, that is for sure, and if you are standing to the side of it, you can feel major air movement coming off of it. But, if you are shooting it, sound and kick are minimal, the brake works very well. I am not a great shot, so I can't speak on accuracy, but I hit what I aim at at 100 yards, I'm sure with good ammo and a good shooter it can do much better.
BTW, the SOCOM 16 and SOCOM II are the same rifle. Don't let the $400 rail fool you, they are exactly the same. You can send a SOCOM 16 to Springfield and have them put the rail on, and now you have a SOCOM II (I called). But the rail is heavy as hell, so I will not be doing that. I like mine the way it is, it is nice and short, as accurate as I am, and has a nasty bark. Love it.
This is a medium range weapon, for CQB and quick longer shots, but not for super long range shooting. I'd say the accuracy is WELL within 4" groups for sure, even when I am using it (I shoot at stationary clays at 100 yards, 1 shot each, and I'm not very good). This "iterations" or "new version" is BS, it is all the same rifle. The early models had a problem with the front sight falling off, but that is all. SOCOM 16 and SOCOM II are the same, except for the rail which is removable (and the engraved name on the side of the rifle).
I have never had a problem with mine, and I didn't clean it for about 400 rounds or more. It has fed everything I gave it, and hits things with authority whenever I use it. Always goes bang, always chambers next round.