Well, that's a good rifle for sure and pretty good ammo, so I've heard. I don't have any experience with either rifle or ammo. I have owned several Sendero's and one actually was in .300WinMag.
Out of the box would be purely speculative as no two factory rifles perform the same. You may get a "hummer" or you might get a turd. Hopefully you will get the better of those two!
You may have to lighten the trigger, don't forget to check the bedding and ensure the action screws are torqued properly (65in/lbs) and do a decent break-in of that new barrel and you shoudl be printing tiny groups in a "few". Sorry so vague but really, who knows?