The 5.6x57 isn't so popular because it has a rather thick neck in order to accommodate the used of sub caliber inserts...
you are absolutely right, the 5.6x57's thick neck is completely abnormal and a nuisance when resizing cases.
otherwise, I like the cartridge very much. my rifle is a Krico that shoots both Sierra's 65gr GK and Barnes' TSX' 62gr quite accurately at 3,600 fps... a very deadly combination.
