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  1. #1
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    Default Glock Rear Sights

    I have been researching Glock rear sights because I was chasing POA = POI.

    Front sights are the standard height but there are 4 different rear sight heights.

    All of my Glocks were bought brand new. After checking the rear sights on each, I discovered the following:

    1) The wrong rear sights were installed on some the pistols.
    2) Most were not centralised on the slide.

    I have corrected this by purchasing the correct standard sights, some metal and some polymer. This has allowed me to achieve fantastic accuracy and consistency with my groupings.

    Generally speaking, Gen 3 and 4 - 9mm, 40S&W, etc use 6.5mm tall rear sights and 45ACP uses 6.9mm tall rear sights.

    Still getting to the Gen 5s.

    Any info or knowledge would be greatly appreciated.

  2. #2
    User Marius@Jizni's Avatar
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    Default Re: Glock Rear Sights

    Quote Originally Posted by jiggajono View Post
    1) The wrong rear sights were installed on some the pistols.
    2) Most were not centralised on the slide.

    Generally speaking, Gen 3 and 4 - 9mm, 40S&W, etc use 6.5mm tall rear sights and 45ACP uses 6.9mm tall rear sights.
    Glocks are shot at the factory and the sights adjusted to POI. If your Glock came from the factory with anything other than 6.5mm, it means the guy at the factory found that the better height for your specific pistol. Same with a sight that is not properly centered (unless it's been bumped).

    We saw the same with the (previous gen) P-07 Duties. They came with plastic sights ranging from #1 to #3. When CZ changed to metal sights, swapping a sight became a mission, so most of them are the same height now.

    I'm not saying never to change heights (hey, that's how I make money), but I would be careful about doing it. Very careful. Personally, I don't even like to change a click on an adjustable sight without a large sample of rounds fired over a bean bag. Preferably over more than one range session. As a rule, I'm also slightly more comfortable with a change to lower the POI, than one to lift it (like changing a 6.1 for a 6.5). If we adjust into even the slightest tendency to push down, we are going to reinforce it.

    Quote Originally Posted by jiggajono View Post
    1) This has allowed me to achieve fantastic accuracy and consistency with my groupings.
    This is, however, an interesting comment - depending on what you mean with consistency. If you refer to shot-to-shot consistency, changing sight heights would not give that to you. If you refer to consistency between different pistols, that would indeed indicate an improvement.

  3. #3
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    Default Re: Glock Rear Sights

    One example was that my G22 Gen 4 came with a 6.1mm rear sight, brand new from the factory It consistently shot low. The correct sight height is 6.5mm. I changed it and now POA = POI.

    Similar story with my G21. Adjusted to the correct rear sight height, 6.9mm, and it's dead on again.

    Consistency between Glock pistols because I don't have to 6'o clock certain models any more. Same sight picture across my Glocks

  4. #4
    Moderator SSP's Avatar
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    Default Re: Glock Rear Sights

    What distance are you testing at?

    What group size are you getting?
    Cattle die, kindred die, every man is mortal:
    But I know one thing that never dies,
    the glory of the great dead.
    Havamal

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    Default Re: Glock Rear Sights

    Using NHSA postal target distances; 8 to 10 metres.
    Under 3cm groups.

  6. #6
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    Default Re: Glock Rear Sights

    Most factories zero at 25.
    Cattle die, kindred die, every man is mortal:
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    the glory of the great dead.
    Havamal

  7. #7
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    Default Re: Glock Rear Sights

    I shoot indoor range regularly. Suppose I have zeroed for my preferred distances. Works nicely.

  8. #8
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    Default Re: Glock Rear Sights

    Handguns should be zeroed at 25m off a dead rest and if itd your carry gun it should be zeroed with your carry ammo.

  9. #9
    User Marius@Jizni's Avatar
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    Default Re: Glock Rear Sights

    I never worry about zeroing distance on an iron-sighted pistol.

    It is running pretty flat, ironically, exactly because it is accelerating downwards so fast. So the 25m zero is actually its second zero point. That places a first zero point somewhere between us and the zero point. Before it, the bullet is rising up from the muzzle which is only 15mm below the front sight, and after that, the bullet is cresting so it is actually running pretty flat. I don't want to stake my reputation on whatever ballistic calculator I could find online, but let's say less than a bullet diameter difference anywhere between 5m and 30m.

    Compare that to the effect of the 0.4mm step in sight heights. One step in rear sights will change the POI about 2.4 inches at 25m, or one inch at 10m. It should be obvious that zero distance would not have a significant distance in sight selection.

    In my opinion, the main reason we experience the effect of distance so bad, is because we overestimate our accuracy at closer ranges. One ragged hole that takes out the bottom of the bulls-eye at 7m appears fine, but at 25m it is no longer one ragged, and three times lower. This looks much worse, but it is actually the result of the same fundamentals.

    (Now, optic sights - that's a different story. The bullet starts further below the sighting pane, which pushes the first zero point to 25m or further. So the bullet rises for most of the way towards the 25m zero point and sight over bore becomes a thing.)

  10. #10
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    Default Re: Glock Rear Sights

    Quote Originally Posted by Marius@Jizni View Post
    In my opinion, the main reason we experience the effect of distance so bad, is because we overestimate our accuracy at closer ranges. One ragged hole that takes out the bottom of the bulls-eye at 7m appears fine, but at 25m it is no longer one ragged, and three times lower. This looks much worse, but it is actually the result of the same fundamentals.
    This. Emphasis added.

    Its easy to conceal mediocre marksmanship at close ranges, especially with larger diameter bullets. I worked at a range back in the day where it was often touted that .45ACP was more accurate than 9mmP because the edges of the holes cut in the paper intersected, whereas the 9mm holes did not. I pointed out that that was only true if one measured groups edge to edge, but it no longer held if you measured center to center. This resulted in blank stares, because it was not dogma.

    To get a real impression of a pistol's accuracy and its POI you need to shoot at 25. I begin and end every practice session (as infrequent as they may be these days) shooting groups at that distance.

    Realistically you can only gain. If you can shoot tight groups at that distance you can shoot tight groups at 7m faster.
    Cattle die, kindred die, every man is mortal:
    But I know one thing that never dies,
    the glory of the great dead.
    Havamal

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