Never shot more than 1000 rounds at one sitting with a wheelgun.
I'd guess maybe 700-800 in an extended morning to afternoon session.
9mm in an semi-auto?
Shot up several thousand in one day.
One of the first things that I did when I got a new dillon 550 was to find a good load, then crank off a whole ammo can full of ammo.
Maybe 3000+ rounds of 124 grain rainiers at 1100 or so, through a pair of CZ75s, a smith 5904, a sigpro 2340 (With bar-sto conversion barrel), and a sig 228, all in the same day.
All at 7 yards at a local range.
Reliability testing can be such a pain can't it?
Load up all the mags I had, then shoot 'em up, change mags as fast as possible, repeat until empty, switch gun, repeat.
There was a matrix style patch of brass littering the area.
I swept it up, and spent most of the evening after the range closed picking up my brass after hours.
People at the range just couldn't figure me out.
That's okay, they'll get it (Eventually.).
I routinely shoot up 500+ rounds in a single session, but I usually like to break up my sessions into a morning session, and an afternoon session.
I wind up shooting better if I take a break after the flinch monster rears his ugly head.