300 Winchester Magum Wildcat

I have a 721 Remington 300 H&H, at one time I thought about rechamberin it to 300 Winchester Magnum and was told since I had the long action, and rechambering the Barrel would require setting back the Barrel to much making the metal to thin around the camber. If I had to do this project a alternative was to rechamber it to 300 winchester magnum, then go in with a 30/06 neck reamer and lengthen the 300 winchester with a 06 neck.. I was also told that while the brass was a wildcat, in a pinch, I could use standard 300 winchester rounds

Can anyone share info about this ..