Originally Posted by kalnaren
If you're using mags that have a separate insert (like KA standard mags) you could try inserting a bit of a "spacer" between the mag insert and the body of the mag to raise the magazine higher in the magwell.
Huh, that's a pretty good idea
I have a bunch of KA mags for my GR16R4. Like the OP, they were a bit sloppy/rattle-y and didn't feed reliably unless you pushed up on the bottom a bit. What I did is cut some lengths of electrical tape to the width of the catch hole in the magazine, slide the insert out slightly so I could get in there, and then just looped three or four wraps of tape upwards, through the hole, over the top of the magazine shell and back down, etc, etc. It bulks out the side of the mag ever so slightly, and also bulks out that hole so that it has to seat higher in the well to catch. I can take some pics if you want...
Now that I think about it, it may have also moved up the insert somewhat as you suggested, but the insert's little tabs still catch on the shell's holes and it stays in place so I dunno...
What I do know is that it's cheap, low-profile, unobtrusive, and works like a charm