"Back in the day" when I was yet a lemming, I followed the horde and acquired both .222 and -.200"/22BR reamers . . . I would not order a .22Cal reamer with smaller than a .248" neck diameter. Yeah, the 'old school' (TIGHT necked) reamers worked, but what was/is the point - turning is merely to accommodate concentricity. I'm pretty certain that, "turn thin to win" means turn for adequate loaded-round/chamber clearance, not thin neck walls for the sake of thinness . . . ;-) RG