Just compiling data that I have randomly on sheets of paper all around :)

J frame ------------------- 1.3125"
J frame magnum ------ 1.34"
SP101 --------------------- 1.35"
K frame ------------------- 1.455"
GP100 --------------------- 1.557"
L frame ------------------- 1.562"
N frame ------------------- 1.712"
Redhawk ------------------- 1.78"
X frame ------------------- 1.92"

X frame widths courtesy:
http://smith-wessonforum.com/s-w-revolvers-1980-present/288271-x-frame-cylinder-width.html

measured 7 guns, all fluted cylinders
ejector ----crane
end --------end ----gun
1.921 -----1.921---460 12"
1.924 -----1.925---460 10 1/2"
1.925 -----1.926---460 8 3/8"
1.920 -----1.920---460 5"
1.920 -----1.920---460 ES
1.923 -----1.923---500 5" JR
1.920 -----1.920---500 5" JR

GP100 and Redhawk courtesy of http://smith-wessonforum.com/s-w-revolvers-1980-present/291958-gp100-cylinder-overall-vs-k-l.html#post136963544 which pointed me here: http://rugerforum.net/ruger-double-action/17967-cylinder-diameter-sp-gp-six-series.html which in turn points you here: http://=http//www.thehighroad.org/showthread.php?t=491314]I%20Gotta%20Tall%20Request%20-%20THR