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This is the gauge
ht tp://www.ebay.com/itm/Rimfire-rim-thickness-measuring-gauge-22LR-22-17-Mach2-Raven-Eye-Custom-Sub-MOA-/321559564853
This is the dial indicator but you can get one from any tool supplier in canada
ht tp://www.ebay.ca/itm/Dial-Indicator-0-1-Inch-Range-0-001-Inch-Graduations-DI-1-/370992245704?hash=item5660dc6bc8:g:4EsAAOSwgApXAoj8
Sorting rims won't make bad ammo shoot well, good ammo is so consistent in rim thickness that measuring is a waste of time. I'd rather spend the money on a nice case of beer...
Rabid is right. Of all the accuracy improving efforts one could undertake, sorting for rim thickness is among the least productive. Get good ammo and practice. That's the surest way to improve results -- assuming the rifle is not compromised by other issues that deserve attention and shooting technique is sound.