I thought Bill preferred .36 caliber Colt Navy revolvers...
You beat me to it.
Hickok did carry a pair of .36 Colt Navy revolvers. A pair, not for the firepower as the author states, but because in the percussion cap and ball era reloading a revolver took some time. He never pulled both revolvers at the same time, the other was a back up.
When Hickok was shot and killed in Deadwood in 1876, the only weapon found on his person was a Smith & Wesson .32 cal rimfire "Old Army" cartridge revolver that was in his coat pocket.
‘Am Shooting Journal’ is not known for historical accuracy.