This is an example of a round padlock.
They are popular because they have a short shank and are harder to get bolt cutters through to cut open.
I have an old master lock discus lock of some sort ( this one, I think ). It definitely rattles a bit as well, but the mechanism isn't flipping in the way that you describe. I found that greater tension helped me get more audible clicks from the pins on my lock anyway. The vice definitely makes things easiest, but I'm assuming you'd rather go by hand. best of luck :)
Buy a high quality padlock. Something like this.