They were somewhat common in the older German and Austrian guns, but seem to have died out, for the most part. I run across an occasional u/o in something like 7X65R or 8X57JRS over 22 hornet, 222, or 22 Savage HP. Common now is to use a small caliber insert in a drilling to make a Bock-Drilling, in essence. I have my Sauer 12/12/30-06 set up as 22 WM/12/30-06. Its a plains game, Francolin/Guinea fowl killing SOB!