I have a sweet deal set up for 3 NIW 30 round
Cooper USGI mags. IIRC, did I hear some negative feedback about these mags, or am I mistaken? I'm sending the $ out tuesday, so quick feedback is greatly appreciated. Thanks guys!

You may want to check out the magazine FAQ section and read the part related to magazines manufactured by Cooper Industries.  Some of the Cooper "USGI" magazines were apparently manufactured out-of-spec, and don't work well in some rifles.

I only have one of the Cooper mags.  It is out-of-spec, but I like it.  Here's why...  It has a very slick, smooth teflon like finish.  This finish is comparable to (perhaps better than) the teflon finished magazines made by Labelle.  Like I mentioned above... my Cooper mag would not pass USGI inspection.  It only has three spot welds (rather than the standard six or seven) and fits very tightly in all of my rifles.  It will not drop free when I push the mag release button.  That's not a good thing for a combat rifle, but I really like it for a range or plinker rifle.  I don't have to worry about accidentally releasing the magazine onto a hard floor.  Despite its tight fit, it is 100% reliable feeding ammo.  I can't say that about all my in spec USGI magazines.

In my mind, if you got a good deal, there's not a lot of risk.  If you get well made, in spec USGI magazines, you will have gotten what you paid for.  If you get out-of-spec magazines, you'll get examples of an historically interesting magazine.  Some collectors are apparently paying a bit of a premium for examples of new Cooper out-of-spec magazines.  Good Luck.

Ive got maybe 5 or 6 Coopers(sorry got too many mags to go dig thru them to see) Anyway,..Some have the correct number of spots and i think maybe 2 of them have 3 spots...1 or 2 of them will not drop free,and all of them function perfectly otherwise. But then agian a have mags from different manufacters and some of them do not drop free either..So i say Buy em' If ya dont like them IM me ill take them off your hands................UNDERDOG

Cooper's .gov contract was recinded. Many of their mags had too few spotwelds on them (2 or 3, as opposed to the 6 they're supposed to have).

My very first set of mags for my very first AR15 were purchased from three different sources, and all were Coopers.  Apparently all dumped on the civilian market at the same time they were removed from military use.

All of mine had 6 spot welds front and back, and the bodies were good.  They would not feed the last 5-7 rounds.  As an experiment I put in a wood spacer to compress the spring, and put in 20 rounds, and they fed all the way to the last round.  Then I removed the spacer and spring, and replaced with springs from my Mini-14 mags, perfect functioning.  

I simply obtained new mags, at that time you could not find replacement springs, after all, NIW were selling for $8.00.

IF the bodies on yours appear to be good, have all the spot welds, I would replace the springs and followers and test them, using them as range mags only until deemed reliable.

I'll echo what I've already heard here about the quality finish on the Coopers...I have a few, even some NIW and they all seem to have an olmost machined look at the top front near the feed lips.  Anyone else look close at theirs and notice that.

All of mine feed real well and drop free and have the mandated 6 welds so I really like them.

Go for the buy if your deal is right.

I have a 6 weld cooper that has an excellent Teflon finish. It meets the other USGI mags Spec. I know I got lucky, and not all Cooper mags are as good.

YMMV

Nobody did teflon finishes on mags at the time Coopers were made.  Perhaps the bodies were changed out.  Or someone swapped floorplates with Labelles, putting Labelle floorplates on Coopers so they could get rid of them.  Who knows?