Neck sizing doesn't work for belted cases; it's not going to produce the best accuracy and most so-resized belted cases won't rechamber in the same rifle anyway. Whenever someone thinks neck sizing does work, I'm convinced they haven't shot enough test groups with enough shots per group to be significantly worthwhile.
Most belted case rifles need their fired cases sized all the way back to the belt by the full-length die. That's because most folks load these cases too hot and the unsupported case immediately in front of the belt expandes enough that it won't chamber fully, even after typical full-length sizing. Most folks think the bolt won't close because the shoulder isn't set back far enough, so they screw the FL die down, then resize again. When this happens, the shoulder gets set back further and further as the die finally gets the body diameter in front of the belt small enough to let the case be chambered. When so-sized cases are fired, the shoulder being back many thousandths from the chamber's shoulder blows forward and the pressure ring thins. After only a few FL sizings and firings using such practices, the case will have a head separation. I'm convinced this is the most common cause of short belted case life so many folks have. The cure is to cut the powder charge a couple of grains and set the FL sizing die in the press only far enough to set the fired case's shoulder back about .001-in. Case life will greatly increase and accuracy will get better, too. Plus, the peak pressures are going to be back down for what the case and rifle was designed for in the first place. Had I not observed dozens of belted case rifles having these case life problems, I would not have believed it to be a reality.