This feels like an action shooting sport in video game form and I love it. It got me excited for tomorrow's match, and boy do I have some opinions for you.
You could borrow a lot more from action shooting sports. Those usually have divisions based on equipment, which you could use to make things like lever rifles more useful, i.e. by giving them their own division along with par times. These could be different on different levels; I ran the Kill House just as fast with a pistol as I could with a rifle, but the Scrap Yard is a very different story.
It isn't clear how many hits the mannequin targets need to go down. Is this explained somewhere and I just missed it? Something simple like, "2 hits with pistol caliber, 1 hit with rifle or shotgun" might be better.
I found the automatic reset at the end of each run unsettling. Why does the weapons autism stop there? It would be much better, I think, to force the player to stop and reset manually. This gives the player a chance to practice the controls as well as create a natural divider between consecutive runs.
The controls feel strange, because the controls for weapon manipulation are handled with the left hand, which handles movement, rather than the right, which otherwise handles weapons. I tried moving the "Charge" button to the middle mouse and that was drastically better. Maybe something with the mouse wheel: back and forward for pump, forward-back for lever, stuff like that. Or hold middle mouse and move in a certain pattern that can be placed over the crosshair like a minigame: up and down in an arc for lever guns, back and forth for linear actions. I don't know what the right answer is, but I think there's a world of interesting possibilities there.
A thought on the HUD: instead of using the fire selector to indicate if the chamber is loaded, maybe split the count between magazine in chamber, like "1|29|60" or "(bullet) | 29 | 60" for 1 in the chamber, 29 in the mag, 60 in reserve. Or you could get rid of ammo counts, but that comes with its own bag of problems.
On Ranch, the level would go black pretty frequently. It happened on-and-off all over the level, but only on that one level.
So anyway. If it sounds like I'm complaining, know that I had a lot of fun playing. Keep up the good work!