Tried the mdt plastics in 2x genuine R700, a nucleus, Archimedes, TL3, and deviant. Horribly draggy feeding in all of them, felt like the case rim was digging into and gouging the feed lips, sometimes it would even chatter the bolt when stripping the round from the mag. You really had to muscle the bolt forward especially for the first 4-5 out of the mag, then the follower tension relaxed a bit and it wasn't so bad. Played with mag height, didn't help. Maybe I got a bad batch but all 5 I bought on black Friday a few years ago had the same issue.
Really wanted the MDT metal 223 mags to work since they are dssf and shorter than the single stack accurates, but a couple of misfeeds with the MDT metals made me miss shots on coyotes so I went back the accurates.
At least we have a few choices and you can pick whatever works best in your rifles. As a disclaimer both my 223 bolt actions are 223AI and that makes them a bit pickier on feeding and presentation angle and release point compared to a standard 223 with a more shallow shoulder angle.