I do not reload any belted cartridges, but I know at least a 1/2 dozen who do they get about four reloadings per case and then they report the accuracy goes south.
From what I have read and what my fellow shooters are telling me regarding the 300 Win mag could all be hog wash
Sorry, but four reloadings per case is hogwash. There is no reason anyone who knows how to reload will not get as many reloads from the .300 WM as they do from any other case. Accuracy does not "go south" after 4 loads.
Accuracy does not go south with any specific case after a few loads if the loader is sizing cases properly for his rifles. You will get split necks and incipient head separations long before accuracy starts to degrade.