I have a winchester M70 stainless in 7mm Mag sitting around & thought I may rechamber it. What are my options ?

I would leave it the way it is.

The 7mm Remington is just about the most perfect Magnum caliber there is for most game in the lower 48.

If you were not happy with it, you would be better off to sell it and just buy what ever you were looking for.

Just about any other mag that you can name.

Pretty much anything you want . Some calibers will requirebolt stop,magazine box and rail modifications .

Not really-you are limited to belted magnum cases no longer than the .300 Win. Mag. Unless you alterred the action to accept longer cartridges.

As noted above, it is hard to improve upon the 7mm Mag.. But one cartridge I would consider is the .308 Norma. Granted, this round has been overlooked for a number of years, but it is probably the best .30-cal. belted round there is. Another possibility would be the .30 Newton, essentially the .308 Norma w/o a belt. I understand Jamison is getting ready to offer brassfor this round.

I designed and developed a new wildcat cartridge that is based on the fulllength .375 ruger case necked down to 7mm. It provides excellent accuracy with high velocities-all in a standard length action. It's a good canidate for your action.,or perhaps I could buy your action?

Stalking Bear, would a reamer foryourcartridgecompletely clean up the 7mm Rem. Mag. chamber? What is its water capacity? If you don't mind.....

Yes it completely cleans up chamber. Water capacity is 98 grains-6% more than .375 h&h.