Well...In taking a look at a few of my friends' CA AEG's, I have notice numerous small differences. I have the CA M15A4 Carbine and my friends have: CA M15A4 Carbine, and CA M15A4 Tactical. First off, I looked at my friend-with-the-Carbine's AEG, and I noticed, on the inside, that his piston was black, and mine is yellow. A little bit strange considering it's the same gun. And when I compared it to the Tactical, There were even bigger differences. First off, obviously it has the full-stock(and the wiring for the full-stock), and that's not what i'm talkin' about. On this AEG, the upper and lower receivers slide apart instead of hinging apart like every other armalite series weapon I've ever seen.(including TM's) Also, the gun came with a metal hop-up unit installed already out-of-the-box. And the new armalite CA AEGs' lower receivers usually are made designed for plastic ones. The order we bought our guns was: 1 ) my friend's carbine; 2 ) my carbine; and 3 ) my friend's tactical. Were there changes in production that weren't announced? Or was I just outta the loop on that one? Or, another possibility, are the inconsistencies normal for AEG's?...I wouldn't think so but then again, I don't know... Oh and we all ordered them stock with no work(upgrades)done on them. Also another note(kinda off this topic's theme) when my friend ordered his carbine, he went ahead and got the 12v 1500mah batt that comes recommended with that gun...It was supposedly made for that gun, but, when we got it we discovered it was a large connection, which didn't fit the carbine's mini-plug w/o a converter wire. we didn't have the converter wire. So he told me, instead of waiting, he'd rather cut off the mini connection that came with it, and have me attach a large one to the gun. so I did, but he made a mistake in cutting the wire, because he did so north of the small plugs that connect the fuse(and extra wire length in the negative wire) to the gearbox wires. So, now when we take his gun apart for maintenance, we can't fully remove the upper receiver from the lower receiver, and we have to work with the two pieces teathered together...not hard to work around, just a bit of an inconvenience...(sry i just had to tell that story...I find I have nothing else to do at 3:20 in the morning
)