I have used them. I will never own one. Most RedDots mount too high for the boresight to work on a pistol. BoreSights work best on rifles if used properly, but the only use is to get the shot on paper. Some people are really good with them and get first shots well within 4" of initial point of aim. (Rifles @ 100yds) I don't know how, since the ones I've used have a bloody 10moa dot.
I prefer the poor man's bore site. Pull the bolt, look down the barrel. Look through the scope. Adjust. It's a little different with most pistols or lever guns. But this is my prefered method for a Ruger MKII. Still, you'd be surprised at how close that scope will be if it was mounted properly. Elevation should be the only major adjustments made.
I did this with a .22 rifle last summer at a 50' target. Adjustments at 50yds were a couple inches up and a half inch left.
Else, I just walk close to the target, shoot off hand, adjust, walk back, shoot, adjust, If needed, walk back, shoot, adjust. Then shoot at my anticipated distance from sand bag or Ransom rest to fine tune. In all my years and several optic guns, I've never shot $40.00 of ammunition doing this.
Now, there is a product that is a laser unit in a dummy cartridge for centerfire. I don't think they make one for .22 rimfire though.
Insert it in the chamber, and when the bolt is closed, the laser lights down range. This would be quite nice if hunting and one just wants to verify that all is well after a scoped rifle, (and the hunter/shooter), slide down a cliff while out Billy Goat hunting.
Hey, don't laugh! I had the internals of a Simmons scope go south on me when the rifle went north when bicycling in to a hunt area. (Roads were closed to motor vehicles). Since then I've been quite happy with my Leupolds!
So, I'll advise not to buy a bore sight for a pistol with a fresh Red Dot. Buy more ammo. You'll have more fun shooting.
-Steve
