Alright Tex I've gotta type fast as I have a computer invasion happening. Ok 1st before I wade into these waters, what does CT say. I'd go with their recommendation first.
Now let's look at the device, the line of sight is below the barrel instead of above like the sights, in most instances the distance from the center of the bore is greater on the grip than on the metallic sights. The laser will only intersect the path of the bullet on the rise and on the fall, 2 places on a hand gun, that may be cool depending on the point blank range of the load, remember each .005" change on the height on the front or rear sight = 1" @25yards on a 5"barrel, and the height of the metallic sights is different from the laser below the bore. kind of like an ar15, with the line of sight so high above the bore, up close it does substantially different than at 100 yrds. I would sight mine in, and have at 15', at 10 yrds it is about 3" high, still ok, and then go range test it, @ 10, 15, 20 and 25 yrds,then document it so I know what to expect. In low light their great, in daylight too hard or long to pickup. I hope this was confusing enough for you, but trying my best.