You can specify if you want a match or field chamber when you buy the rifle, that's what's usually offered. Where you might be confused is when it comes to bench rest rifles. They offer different types of chambers for the customer, one being a bore rider. That and they will also tighen up the neck area of the chamber for better accuracy.
That means that a match/hybrid, match and bore rider, you'll need to turn the necks as regular off the shelf brass won't fit because the necks will be to large. If you just want to bust rocks and do some other plinking, go with a standard chamber. That way you can shoot surplus ammo or reload surplus brass and not worry about turning the necks.
Some die makers do have inserts to resize the necks if you have a match chamber. This way guys can specify what they want when they order their dies. With a standard chamber and standard dies for reloading it will resize them back to the original case specs set for the original military cartridge.
