There's one (NR) in the EE now. The early AO's had 'bad' springs, inthe Rifle itself. Reveiws of early models were hit n miss. People reported changing springs on those earlier ones, & rifle functioned very relaibly. I don't know the cut off, but, anything more-so manufactired in the last 10 years form AO, has better quality internal springs. Reviews seem good.
Also to ad, the Original GI mags, on the batte field were practically considered 'Throw away'/not a multi use item.. Think it was due to the springs. There's Documentries on utube that mention this.
Newly made Korean magz, seem to be the best of what's currently 'new' out there. {15 & 30 rnd available}