For a true double feed -- two live rounds one fully, the other partially out of the magazine -- its got to be a magazine issue or the OP has experienced something really weird and unique.
Perhaps he's confused Pro-Mags with Pmags?
Lots of folks mistakingly call a failure to extract -- fired empty still in the chamber, live round jammed in behind it trying to feed -- a double feed.
I'm of the opinion that if your gun fails to extract with steel cased ammo but does with brass cased ammo, blaming the ammo is ignoring the real issue -- your gun has no operating margin and I'd never trust it under harsh conditions. When I've seen this, its always been an out of spec extractor -- either gap between the hook and the bolt face too small to fully slip into the extraction groove, or the front of the hook was too fat, again preventing the hook from fully fitting into the groove.
I also believe that if you pay top dollar for a supposedly "match accurate" AR, feeding it Wolf kind of defeats the whole purpose as its 2 moa ammo in its best lots, but if it doesn't work with steel cased ammo, best to forget any delusions of having a battle or TEOTWAWKI ready weapon.