Well, it is hard for me to believe that there was such an animal in the war. Hoss Cartwright could not have handled such a pistol. It was a formidable round but only found in rifle caliber & not in a pistol. One also has to remember as to when did McCorkle make this statement? Most likely late in life & memories do fade.
It is a known fact that when these veterans started giving interviews, a lot of them would stretch the truth a wee bit plus, age has a way of clouding memories.
I am in the camp with Leslie, that it was the Savage revolver. It was indeed a muzzle heavy weapon but, granted, was in .36 cal. Yet, we know the cavalry did carry these behemoth's & 11000 of these weapons were purchased by the army.
An earlier post stated that they possibly were armed with Starr revolvers. This was a cumbersome pistol in that it was a double action pistol in both .36 & .44 & those not use to firing a double action would have a tendency to pull the barrel down when firing double action & thus undershooting a target. That being said, the Starr was widely accepted & was an easy weapon to load & break down to clean. The Government did request that Starr design a Single Action pistol that would cost less.
The single action Starr revolver had an 8" barrel which might be considered muzzle heavy but this skirmish took place before the single action Starr came on the scene.
As I say, only Springfield Research Service possibly could shed some light on this matter.
Anyway, an interesting question to ponder.