I use a Panavise with plastic jaws.
There's a reason for that: you can't accurately sight in a pistol with a laser, you can only get it close. The pistol has recoil and the muzzle rotates upward in an arc when you fire. That means if you sight the bore in onto intended point of impact, you will hit high on the target. BTW, revolvers have much more of a "POI shift" than autos since the moving slide of an auto absorbs some recoil.
For a ballpark, I have used a laser and with a typical .357 shooting 158 grain .38 sp ammo, the bore should be aligned about 3" below sight line @ 25 yards to hit POA. This will vary by shooter and ammo since it is affected by the gun's muzzle flip.
For the record, most of my 9mm autos will hit POA with the bore aligned about 1 - 2" below sight line.