If the brass you're using was only ever fired in one rifle and it was your rifle and it will only ever be fired in that one rifle of yours, the belt isn't that big of a deal. If say, for example, your 300 win mag brass was first shot in a military sniper rifle because perhaps there was an ammo panic going on and that was the only brass you could find, you're going to find out that the belt will prevent you from fully resizing some of those cases and so a percentage of your cases simply will not size down to fit your rifle's chamber. You can then spend another $100 on the Larry Willis die which will fix a percentage of those cases but it may be a small percentage of them so of the 100 mil surp 300 win mag cases you bought, you may end up with 50 cases that will chamber in your rifle and so, after spending a bunch of time and money trying to make this brass work, you may come to the conclusion that the belt is completely unnecessary and, worse, can be an inconvenience for the reloader and you may just start looking at the 30/06 or at one of the newer non-belted magnum calibers like 300 RUM.