I had the same problem with mine when I got it back from the factory with a new ML barrel. Like you said, there is excessive gap between the frame breech face and the rear of the breech plug. A thicker primer holder would solve the problem. Until it's fixed, you will get misfires and blowback making a mess, including getting back into the action around the firing pin. A half assed fix that may work is just pushing the primer partially into the holder (not seating it all the way in). This may get you through the season until you can send it back. Not sure what NEF would do to fix it. This is another reason why the frame has to be sent back for each new barrel (not the best QC in terms of dimensions). Using a very thin machine washer (close to .040 in your case) in front of the shoulder of the breech plug may set the plug back enough to close the gap. What I did was get the 25 ACP breech plug. Yes, it cost $60, but I got it in 2 days and it fixed the problem. There is more than one solution to a problem. Good luck!