Under 200 yards the Whelen does not compare to any 300 mag. It just kills faster and better. Frontal area matters. Past 200 yards there probably isn't much difference.
2700 FPS should be very easy with any 225gr bullet, even with the older powders.
I've had good luck with several JES rebores he's done for me and I've bought several JES rebores that other people have had done and they were all great.
