Pistols Of the World by Ian Hogg details the changes in the "C96" including the pitch of the rifling, but it uses a standard that I'm not familiar with...
Quote -
"About 1903...the pitch of rifling was changed from the earlier 1/26 calibres to 1/18 in an endeavor to assure better stability"...And -
"...Next major change...came in 1912...barrel...was now rifled with six grooves instead of four and with a twist of 1/25"...
I don't know the context of twist being measured in 'calibres'...Hogg was English, it may be an English rifling/twist measurement...
Hmmmm...From the
Encyclopedia Britannica -
"The number of calibres is determined by dividing the length of the bore (from muzzle to breech face) by the bore diameter." I'll leave it to you to figure that out...
