I have an older mauser commercial sporter in 7X64. Have not checked the throat, but the rifle shows that it was carried and shot a fair bit...

shoots OK, but.... wonder what a rechamber to a longer cartrige would do?

7 X 64 Ackley wouldn't be any longer then the regular 7 X 64. Setting the barrel back will lessen the effective wear in the throat, if you want a longer cartridge, you have to go to a magnum or a wildcat (or the poor underestimated 280 Ross). Keep in mind that if you go to a longer cartridge the receiver opening, magazine box, and feeding will all become issues you'll have to deal with. - Dan

Art Bourne of Kamloops shot a 7x64 improved for a time. It was, of course, much the same as the 280AI.
Your commercial mauser is likely chambered with the long tapered throat which is common to many European rifles. It looks worn out before it starts! They usually shoot very well though.
The 7x64 is such a good cartridge that it would be difficult to actually improve on it without going to considerable expense. Even then you would end up with what would be termed a change rather than an improvement. Regards, Bill.

It would be the exact same round as the 280 IMP. once the body and shoulder were blown out.