Any info on this caliber seen a used Weatherby in this caliber thinking about getting I currently use a 7mm mag or a 300 ultra mag how does it compare to these?

well since its a 30-06 necked up slightly it will have higher initial velocites but drop off quicker. and it will handle heavier bullets better than the 06.
i think for out to 300yards or so it will make a great deer/elk rifle

Knowing now thay you own a 300 RUM I would go with a 340 Wby Mag. Good luck.