the action came off a new 300 win adl, i bought new floor plate and spring and follower from midway, as far as the bolt head goes i believe it is the same for a um and a mag the only difference i know of is the mag action will not let a ultra mag case go down in the magazine. Sorry for any confusion
If the rifle was originally chambered in 300 Win, it will most likely work without modification for ultra mag cartridges.
The only modification it might possibly need is for feeding from the magazine. Some folks open up the rails slightly, some folks lower the angle of the feed ramp slightly.
Bolt faces are the same between standard magnums and ultra mag.