I just checked several more frames, some old, some new, they all measure .370". I checked several bullets to see if my Lyman caliper is off, it appears right on using the same part of the blade as when measuring the pin. I did notice that if the caliper is canted just a shade, you'll get ~.375" since I'm measuring with just the tip and not the flat part of the blades, but making sure it's square to the pin will get the minimum measurement of .370". :wink: