I am exploring ways to alter the headspacing of my Urutau upper/barrel. The cartridge sits too shallowly in the upper, not flush as the documentation describes. The instructions advise to purchase a new barrel in order to rectify headspacing issues, but I feel that's a little extreme. For context, I purchased a barrel from MAF instead of trying to ECM one. My instinct is to sand down the mounting recess of the upper in order to bring the cartridge flush with the interior wall, but there is already scant material in that area. I'm not sure how necessary the material thickness is. Would it be better to sand down the metal of the barrel instead? I've included a picture of the upper barrel recess. I will say, this area did not print well, and the supports were difficult to remove.