Let's say 150 rounds per hour, but that's really top-end and will bring lots of shrill laughter from the sidelines. It could be as low as 30-40 RPH, but it depends on a lot of things.
Much of your time is spent in setup - ensuring that your cartridge overall length is correct and adjusting the seating die to make it so, setting up a powder thrower so it throws the right weight of the right powder, cleaning cases, calibrating scales, etc.
So, 150, with no distractions, no wheels coming off the track and with some experience, provided that:
- you're not aiming for high-precision, super-accurate loads, just average-Joe ammo
- you're satisfied that the overall length of your cases is OK and you're not contemplating trimming them or deburring them
- you have already cleaned the crud off the cases with something like a rag soaked in lighter fluid
- you have already inspected the cases for splits, etc
- you do all the following steps in one operation - decapping, mouth belling, repriming
- you are using an automatic (tube) primer feeder and it's ideally already full when you start
- you use a powder thrower instead of weighing each charge individually and that thrower is already filled and adjusted
- if crimping is required (not for 9 x 19mm but, say, .357 Mag), you seat and crimp in one operation
Is that all realistic? Probably not, but I have tried to isolate just the loading process vice the fiddly setup. With setup, for 9mm, I would say I normally do better than one a minute.
There are some shortcuts you will discover. For instance, the 9mm sizing die I use has the locking ring cinched down on the die. I don't have to adjust it each time because it's already adjusted and all I need to do is screw it into place and once in a while make sure it hasn't worked loose. Wouldn't do that for super-precision loads, but it works well enough for routine target-busters.
If all you are reloading is one calibre, one load, not much will change on your setup and things will go much faster. If, say, you are using different calibres, different propellants and different bullets, you are going to have to change things around each time.