The belt is a legacy of the 300 and 375 H&H cartridges which most magnums are based on. Roy Weatherby used it as a marketing gimmick inventing the term "belted magnum" and Remington and Winchester stupidly went along. All of the modern magnums, the 264, 300, 338 Winchesters, the 7mm and 350 Remington magnums could and should have been sans belt. The belt makes the cartridge more difficult and costly to manufacture, adds at least two draws to the process and the the more complex cartridge inevitably cannot be made as precise as a straight case with the same care applied. As far as the belt making the case stronger, it adds an inside corner which an engineer calls a "stress riser" to both the case and chamber. And steel has to be removed from the barrel to make way for the belt. The cartridge is supposed to headspace on the belt but almost anyone who reloads the cartridges agrees that they should headspace on the shoulder. You will get into problems reloading belted cartridges when the loads are so hot as to expand the belt. I personally don't load that hot but if you do you may find that the cartridges will not chamber after two or three reloadings and have to be discarded or sized with a special collet type sizer. Another problem is that the belt is always eccentric with the case body, sometimes by several thousanths. As far as accuracy, no one who is ultra-serious about it has used belted cases in decades, bench rest shooters, silhouette shooters, none of them use belted cases. And notice all the modern designs are beltless, the short mags, the ultra mags, all of them. And belted cases don't feed from the magazine as well as non-belted cases. I shoot the 300 Win mag and will continue to but I don't think I will ever own another rifle shooting a belted cartridge except the 458 which I have and which needs a belt. I want a 416 and I am holding out for a Rigby versus a Remington for that reason.
Another thing is I don't like the belt. They are unnecessary, costly and harmful to accuracy and reloadibility.
