I had some CA Mp5 mags, and they didn't fit right, they scratched the magwell and left huge lines, built to sh*t, and were noisy. And everyone I've seen that has had CA hicaps for the m4 variants, sometimes, it takes about 3 people to yank them out of the magwell, but for some reason, they slip in like a brease. The TM mags.. I've never had a problem with. But, my recent AK one (You were there when I got it yesterday) skips a shot every 20 or so shots. I still say, go for TM. It's super easy to lube those up.