I just checked, and you’re right! That’s an interesting discovery. Given that Micah defaultly uses two Double-action Revolvers, it’s possible that they didn’t change the sound for when he uses the Cattleman, but who knows? It’s in a cutscene, too, which may make this more likely.

As far as I know, this is the only gun-sound mistake in the game.

Nah, it happens multiple time's in the story. One example being in "An American Pastoral Scene". Sometimes they even use a different gun sound.

Oh right. I guess I haven’t noticed.

It actually happens in most R* games.

Example : In the mission "I fought the Law..." in GTA V, when Franklin opens the door of his red F620 in the cutscene at the gas station, the sound used is an opening door car sound used for the 3D Universe of the GTA video game series.

Another example : In the mission "The Long Stretch" (in GTA V), during the cutscene at the recycling plant, the sound used for the pistol is different and more realistic.

You have a good eye...er... "Dead eye"....lol