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Used GTL21

Discussion in 'Sights, Optics and Lasers' started by norton, Oct 7, 2010.

  1. I just picked up a used GTL 21. W/O a manual of course.
    Can anyone tell me which of the two screws at the front of the site adjust for windage and elevation. Also which direction to turn them?
  2. RayB

    RayB Retired Member

    Dec 2, 2005
    No, I can't answer your question specifically.

    But what I can do is to explain how to collimate (align) the laser, as the basic approach is always the same.

    If you mount the light/laser on the pistol frame, and sight in a target with the guns open sights, mark where the laser dot is with regard to the sight picture, and begin slowly tweaking one set screw at a time, you will quickly determine which screw moves the laser in which direction, and how much. Most likely, the screw at the front of the laser adjusts windage, and the screw towards the rear adjusts elevation. But no matter...

    Laser Sight Collimation: Pistol

    If you think about it, there's only two ways to collimate a laser designator...

    1) Sweet Spot: The laser is set to converge with the bullet at a distance predetermined by the shooter--the sweet spot. The laser’s point of aim (POA) will be offset more or less, inside or outside the selected sweet spot’s point of impact (POI). This is really the only way to set up the laser/light combos, where the laser emitter is far from the gun’s bore axis.

    2) Parallel Beam or Offset: If the laser emitter sits close to the gun’s bore axis, it can be set up to run parallel to the bullet's path, out to practical shooting ranges. The offset--say it's a half inch--is a known value, and is ignored or compensated for by the shooter. This is how the LaserMax guide rod lasers are set up, since the laser emitter is so close to the bore axis, and it can also be used with the LaserMax Uni-Max and Viridian lasers.

    Both approaches work, and are plenty accurate for self-defense. Neither is designed for precision sniping.

    Good luck! :wavey:


  3. I took my 17 with laser out to the range today. Got out early, before the bay I chose was flooded with sunlight.
    What a hoot! Shooting 7 to 10 yards. Took some experimentation, but I got it hitting about POA.
    Now I am wondering? Do you guys aim down the barrel through the fixed sites to the dot, or do you just center the dot with the barrel lower then eye level?
  4. RayB

    RayB Retired Member

    Dec 2, 2005

    One of the big advantages of a laser designator is that you don't have to sight down the barrel to hold zero on a perp or target!

    You are free to use your binocular vision to scan a room, locate your cell phone--whatever!

    You may also be able to free one hand to dial 911, open a door, release the dog, or if you're really cool under stress--finish your hotdog!

    But take great care when choosing a tactic... A cop or a soldier may take an entirely different approach than you should, in your own home say...

    Lasers and weapon lights require training and practice drills to use most effectively, and safely.

    If you can, get your hands on the excellent DVD feature by Crimson Trace, Shots In The Dark.

    Pray you never need any of it!