I have a new mould for my 9.3. The gascheck shank measures .352" diameter in a fairly soft alloy 95% lead, 3% tin & 2% antimony.
Hornady .375 gaschecks crimp on easily in my Lyman 450 sizer and are firmly crimped.
I do have to say though my 9.3 has an oversize .370" bore and the mould casts at.3725" diameter. My sizing die is .372" diameter so not much different than a standard .375.
I will post results in a new thread when I have data.