Sounds like you need to leave the slide locked to the rear for a week or two and try again. Sometimes factory springs are a tad on the heavy side, and while an engineer will tell you that springs left in their compressed state will not lose strength it seems like this is a good place to start.
Another good thing to do is disassemble, clean, and reassemble the pistol and pay close attention to "wipe marks" where copper or brass is left on the steel. I had a 45 that needed some polishing on the feed ramp before it would digest factory fodder reliably, and I didn't want to wait for the "natural break in" to occur.
Or you could just shoot 300 rounds of Federal through your pistol and then try WWB again, that should give it the break in required.
Machine guns are awesome until you have to carry one.