I can attest to this, because I have a Magpul lower and Vltor upper G&P WOC.
The mags are all tight, especially the PMAGS but they work very well on mine. You have the option to file down your magwell (internal) but then you risk having wobbling effect on other type of mags.
I have bought a bunch of Pro-Win mags. I am selling some let me know how many you need and maybe we can work out a deal.