Co-witness iron sight "windage" to red dot?

[DirtyDigz 1,339]

I put a red dot optic on a G19 with stock sights, took it to the range and then "zeroed" the red dot and was getting hits very close to point of aim.

I then bought some "suppressor height" iron sights and put them on.  Haven't been back to the range yet.

Right now, when I line up the irons, the "previously zeroed" red dot is off to the right per image below (red circle is approximate position of the red dot):


 

Which way should I drift the rear sight, left or right, to bring the irons in alignment with the red dot?

My brain just won't work right when I'm trying to think this through.  I'm thinking the red dot is to the RIGHT of the current irons alignment, so I need to drift the rear iron LEFT, but the more I think about it the more confused I'm making myself.

[High Exposure 4,951]

Do not do that.

Your irons and your dot may not cowitness. That’s OK!

Go to the range. Leave the dot off and shoot the irons. If necessary, make windage adjustments until you are happy with the results.

Then turn the dot on and shoot the dot. If necessary, make appropriate adjustments until you are happy with the results. Then leave it alone!

Don’t move stuff without verifying it has to move.

[DirtyDigz 1,339]

Thanks. My brain is now confused as to how the dot and the irons point-of-aim can be off and still have the same point-of-impact, but I'll try shooting each separately and report back.

[High Exposure 4,951]

• Machining on the housing of the dot could be off

• Placement of mounting holes in the slide or on the dot could be machined incorrectly 

• Alignment of the glass in the housing could be off

•  Machining of the mounting pocket in the slide could be off

• Bosses/lugs could be off

• Front sight placement hole could be off

• You could have an undiagnosed eye issue

• Bad mounting plate (if you are using one)

Those are just a few. There are dozens of interfaces between the optic and the slide and the irons and the slide that could have variances near the extreme end of acceptable tolerances, or even outside accepted tolerances. Combine a couple of those inconsistencies and when the errors are stacked, weird shit happens!

I have some dot guns that are right on, the dot sits precisely at the tip of the iron sight. Others are higher or lower, left or right.

Now, this will really make your head hurt - you may have different zeros now, but that may change over time. In a year, as your ability with the dot gets better, you may even see your zero change to be closer to irons, as you are not having to dial in corrective windage or elevation changes to compensate for other deficiencies.

In the end, all that matters is: You hit what you are aiming at right now.

 

[High Exposure 4,951]

 

[Mr.Stu 967]

5 hours ago, High Exposure said:

• Machining on the housing of the dot could be off

• Placement of mounting holes in the slide or on the dot could be machined incorrectly 

• Alignment of the glass in the housing could be off

•  Machining of the mounting pocket in the slide could be off

• Bosses/lugs could be off

• Front sight placement hole could be off

• You could have an undiagnosed eye issue

• Bad mounting plate (if you are using one)

Those are just a few. There are dozens of interfaces between the optic and the slide and the irons and the slide that could have variances near the extreme end of acceptable tolerances, or even outside accepted tolerances. Combine a couple of those inconsistencies and when the errors are stacked, weird shit happens!

I have some dot guns that are right on, the dot sits precisely at the tip of the iron sight. Others are higher or lower, left or right.

Now, this will really make your head hurt - you may have different zeros now, but that may change over time. In a year, as your ability with the dot gets better, you may even see your zero change to be closer to irons, as you are not having to dial in corrective windage or elevation changes to compensate for other deficiencies.

In the end, all that matters is: You hit what you are aiming at right now.

 

One more thing...that "zero parallax" optic...isn't. 

[High Exposure 4,951]

I will also say this - unless you are a solid 300 5X B8 shooter at 25 yards, don’t zero at the 25. It is an exercise in frustration.

Zero at the 10 (there is less than an inch difference vertically between a 10 and 25 yard zero). You will save time, ammo and frustration by going to the ten, and getting the best zero you can. If you’re shooting well, back up in 5 yards increments and adjust windage. 

[DirtyDigz 1,339]

1 hour ago, High Exposure said:

I will also say this - unless you are a solid 300 5X B8 shooter at 25 yards, don’t zero at the 25. It is an exercise in frustration.

Zero at the 10 (there is less than an inch difference vertically between a 10 and 25 yard zero). You will save time, ammo and frustration by going to the ten, and getting the best zero you can. If you’re shooting well, back up in 5 yards increments and adjust windage. 

Yup, going to use the "25 zero at 10 yards" target recommended in the videos you linked:

 

KC Pistol_Rifle 10yd Zero Target (1.5 Mount) V2.pdf

[High Exposure 4,951]

Unless you are a 1” group at 25 yard shooter, that target is just going to get you chasing your zero all day long with no confidence in it when you run out of ammo.

Use a standard B8 (download and print them out) and keep them all in the 10 ring at 10 yards (all in the X if your feeling froggy) and that is sufficient. Then walk back and confirm. I like to confirm at 15, 20 and 25yards.

If they are all in the black, and evenly distributed, at 25 I’m happy. I may make a windage adjustment during confirmation if I see I am favoring left or right of center.