If you're replacing the rings anyway, why not use a Dremel tool with a small cutoff wheel to remove the old rings in a few pieces? Getting the new ones in should be a much easier task than removing the old ones. Making some sort of staking tool with a pair of vise grips and a pointed setscrew shouldn't be much of a problem- - - -similar to the tool that's used to stake the safety spring tube in place when rebuilding a 1911 .45 automatic pistol.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!