IMHO, it is not a matter of "breaking in" a new gun, but a matter of reliability testing.
On ANY new gun, I recommend firing at least 200 rounds. It should fire those 200 rounds without any failure of any kind (barring bad ammo). If it doesn't, and you think it needs broken in, start the 200 round count over. If it won't fire 200 consecutive rounds without a problem (most good revolvers will fire thousands of rounds without a problem), take it back, have it fixed, trade it off, or put it in the garbage can, but DON'T depend on it for serious purposes.
Again, IMHO, a manufacturer who tells you that his guns won't work out of the box, but need "breaking in" is just hoping you will "break in" the junk until the warranty expires. I would not buy from that maker.
(I MIGHT make an exception for pure target guns, but even they should work, even if not as well as after being broken in.)
Jim