Surprised to see this, compared to your previous downloads- it's a big jump in quality.
Recommendations:
The AR is ridiculously busted at high upgrades. Perhaps focus less on mag size, and swap it for reload speed?
Allow the player to pick up items when reloading!
Shorten the deadzone during/after reloads, especially with the shotgun- having 'finished' the reload, and having to wait a full second+ to fire afterwards is a slowly-annoying occurence!
Give us a button to throw items we're holding- I'd like to be able to move pills away from places like spawnpoints.
Maybe make the between-round time a little longer! Games like KF1/2 give you nearly a minute.
Perhaps consider in-round purchases, like the game above!
On that note, it should be (seemingly) easy to add things like damage resistance, speed upgrades, health maximum, and perhaps small ammo-drops from enemies. Hope this sees continued development!