About 1,000 through my S&W 620, but it's only a year old.
As for the rifle with the most # of rounds through it--either my M1 Garand or M1 Carbine, with an unknown # of rounds through, but my Garand has a new barrel and was a July '42, so it probably has a few more than the Carbine (with the original barrel).
Of course, my 10/22 has had about 2000 through it, no problem.