I bought 10 or 12 C Products mags in a big "group buy" 18 months to two years ago or so.
I wound up sending most of them back after a visual inspection and a simple loading test.
All of the mags had sloppy welds, some better then others. When I loaded the mags to 28 rounds I had the followers jam up on a couple. And these were the Magpul followers!
On one mag, which actually looked "good", the loaded rounds popped out of the mag when I lightly tapped it on the carpeted floor to seat the rounds. I'd never had this happen before with any kind of mag and believe me, I wasn't tapping very hard. I kept tapping to see what would happen and with every tap another round or two popped out until the mag was empty.
I wound up sending them back to the vendor and then paying extra for USGI NHMG mags instead. I did keep three or four of the best looking CP mags to see how they'd run. (I don't know the answer to that yet as while I did have some mag malfunctions in a rifle class, I wasn't able to look to see which mags were bad at the time. Just too busy doing the drills).
Here's some pictures of some of the mags from my order. These were pretty typical of what I received. These were all brand new mags that had never beenn put into a rifle and I only loaded once.
Here's three mags showing the bad metal folds and welds on all three. The mag in the middle is about the best of the CP mags I received.
In this picture I put an OKAY GI mag in the middle. Notice how much cleaner the fold and weld is in the GI mag then the CP mags on either side. That really tells the story right there.