Most states have a Minimum for elk as the 243. Yes the 25-06 has been used with good results by good hunters. The 6.5x55 and the 260 would be the next step up in caliber. Thes would be more effective with their heavier bullets of high SD. I have seen a elk pile up in a hurry from the 260 Remwith a 140 grain X bullet. This was well past 300 yards and the bullet exited threough the opposite front shoulder.