If you're referring to Defensive Edge's +P throat, you do know it has absolutely 100% nothing to do with freebore, right?
Long Freebore- bore rider - +p = All the same concept . Run a throater into the chamber and remove short length of part or all of the lands so bullet has less initial resistance creating a slower pressure ramp. Weatherby takes all the lands out for 3/8”, bore rider a little less, +p only half the lands removed.