I just got a mark II with the standard weight stainless barrel yesterday, and noticed feeding problems right away. Upon searching this site and others, most agree the magazines are usually the culprit. Though I'm not impressed by the fit of the magazine, it turned out not to be the culprit in my case. I noticed difficulty pushing the rounds in, and also scratching of the bullets that had not even been chambered.
The udnerside of the bolt was digging into the round below the one being chambered as the bolt was pushed forward. I removed the bolt and rounded the leading edge slightly. Be very carefull, the metal was softer than I expected, I used light pressure and a fine knife sharpening stone. I removed a small bit, tried it and then a little more until it fed the rounds smoothly. Here are some "after" pictures, I didn't think of taking "before" shots.
I could feel a sharp edge before doing the honing on the stone. It's smooth now. I would advise not to remove much material, it's a lot harder to put it back than take it away.
Hope this helps, a 10 min fix did the trick for me.