I played this a couple of hours back and I gotta say, it's a lota fun. It totally reminded me of playing FPS's way back in the early 1990's when they first came out such as Redneck Rampage, Corridoor7, Wolfensteiiiiiin and the rest. The only issue I had was the mouse was a tad sensitive but I couldn't be bothered looking at the options but I got on with the training mode and level 2 and will be going back some more action.
Have you had a chance to have a look at https://narayangames.itch.io/western-fps? That's another cool FPS.