If you did the search, you've read all Ihave to say on the subject. I would be more than surprised if Marlin/NEF has done anything about this, as they've known about the problem for several years and folks are still complaining about it. Problem is that there are no SAMMI specs for the 38-55, so each manufactuer is free to do as they choose. If it makes you feel any better, Winchester has the same problem and is in the same denial that Marlin is. A classic case of CYA engineering, if the ammo don't fit, the gun can't be fired and there will be no lawsuits :roll:
Actually, I've found the "problem" to be as much as asset as a problem, as have several other shooters here. I ran an experiment and haev a group of cases that was fired 40 times before a neck split appeared. That case could be easily trimmed, annealed and fired more. The tight chamber has allowed me to side step full length sizing almost completely, extending my brass life emmensly. The question is of course what size bore will you have? That is as important as the chamber size. If my bore as was large as .381 as has been reported in a Marlin 38-55 lever, I'd have to have my chamber reamed.
I went into the 38-55 knowing these problems and willing to search out a solution. I got lucky and the solution presented itself by following the methods others had used on both the NEF and the Marlin.
You can trust me on this, the 38-55 is well worth the effort of getting it set up right. It is the sing'e best mild to wild cartridge I have ever fired. I'll not be without one. It is one of those rare examples of something being more than it appears to be.