Howdy
I had to dig out my copy of Kopec's A Study of the Colt Single Action Army Revolver to get you an answer.
There were two slightly different versions of the Bisley Model, the Bisley Target Model, sometimes called the Flat Top version and the Standard Bisley Model.
The first Bisley Target models were shipped to Colt's London agency in May of 1894. These revolvers were designed for the pistol target matches held at the Bisley range outside of London. They were designed purely as target revolvers, meant to compete with the other popular target revolvers of the day, most likely the Smith and Wesson New Model Number Three, which had been setting records since 1878. The Bisley Target model had a drift adjustable rear sight, and an interchangeable pinned front sight insert. The overwhelming majority of Bisley Target models had 7 1/2" barrels. Other barrel lengths were available, there is a photo in Kopec's book of a rare pair of 3 1/2" 'Sheriff Model' Bisley's without ejector rods. The balance of Bisley Target models had the standard 5 1/2" and 4 3/4" barrels.
Since the Bisley Target model was originally designed for the British market, it is not surprising that the most popular caliber was the .455 Eley, followed in order by 32-20, 44 Russian, 38-40, 45 Colt, 38 Colt, 44-40, 38-44 S&W, 32 Colt, 32 S&W, 32-44 S&W, 41 Colt, 38 S&W, and 32 Colt New Police.
These photos of a Bisley Target model are from the Rock Island Auction Company.
Here is a closeup of the rear sight of this Bisley Target model. Notice the Flat Top.
The Standard Bisley Model lacked the adjustable rear sight and had a standard front sight soldered onto the front of the barrel. The Standard Bisley Model lacked the Flat Top, the rear sight being a groove milled into the top strap just like any other Single Action Army.
According to Kopec, 62% of surveyed Standard Bisley models had 4 3/4" barrels, 20% had 5 1/2" barrels, and 18% had 7 1/2" barrels. Kopec notes these are survey percentages of existing Standard Bisley revolvers, not hard numbers from the factory. Kopec also notes that caliber preferences for Standard Bisley models were quite different than for standard Single Action Army revolvers. In descending order of preference, they were 32-20, 38-40, 45 Colt, 44-40, and 41 Colt. Limited production included 38 Colt, 455 Eley, 32 Colt, and 44 Russian.
This 4 3/4" 38-40 Standard Bisley was made in 1909. Thanks for making me look up this information, now I know it is just about the most common configuration of the Standard Bisley model. And the hard rubber grips are standard too.
Notice the typical barrel marking. Almost worn away (BISLEY MODEL) followed by the caliber.
Just for fun, here is a photo of Pancho Villa with his favorite revolver, a Bisley Colt made in 1912.