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Discussion Starter · #1 · (Edited)
A bit of history first…. When I got my Sub 2K (gen 1) I replaced the plastic red slab piece that served as the front sight post with the fiber optic version from TK, then zeroed it at 25 yards (the maximum distance of my indoor range). I then modded the forearm to be able to put on a quick detach red dot, which I zeroed to 35 feet. I figured between the two I can cover close range and "far" range. The thing was, if I wanted to switch between the two I'd have to take the red dot off or put it on as the case may be. Though it's on a quick detach base, it still takes time as I'd have to put the red dot away safely or take it out from where I was storing it.

So I wanted to figure out a way of being able to adjust my aim on the fly for differing distances. I could guess using Kentucky windage, but I wanted a way that depended less on guessing and was also more repeatably accurate.

First things I did were to drill out the hole of the rear sight a bit bigger so that I can acquire the front sight quicker and also allow me not to have to squish my face down so much to see through the hole. I then used a small round file to file a notch at the top of the rear sight. This now gives me two set elevations for the rear. I also added a white stripe to help center align the front sight more quickly.



Using a laser ammo, which is basically a bore laser that flashes a dot on the target when you pull the trigger and the striker hits it, I adjusted the depth of the top groove so that when the front sight is placed in the groove, I'm zeroed at about 15 feet. I was doing this at home so this is about half the length of my house. So now I can switch on the fly between home close in defense and outdoor farther away defense by whether I place the front sight in the top groove or in the hole.


Then, just out of curiosity, I painted a white dot below the front sight to test what distances those zero at when I use that dot in the hole or the notch.

(Yes, my front sight does have to be that far right for the windage; the factory sight came in canted to the left.)

What I found was that when I put the lower white dot in the hole, it placed the red fiber optic in the notch, so no additional benefit in aiming using the white dot in the hole when aiming using the red fiber in the notch does the same thing.

When the white dot is in the notch, the laser ammo would hit where that white dot was when the target is at 6 feet, or basically half the distance of an average room in my house. That's not all that useful in a defense situation since at that short a distance just shouldering the carbine and point shooting would do. But the interesting thing was that if I were to just quickly shoulder my Sub 2K naturally so that my cheek is comfortably pressed to the buffer tube and my head held in a relaxed non stooped position, this places the white dot right in the notch. So white dot in the notch by accident is the same head position as a quick point shoot shouldering within the room distances.

But even more useful was that at 15 feet distance, when the white dot is in the notch, the point of impact is where the red fiber optic is. So for those ~15 feet indoor distances, I can either put the red fiber optic in the notch and stoop my head a bit, or I can relax my head to see more of the surroundings by placing the white dot in the notch. Either will give point of impact at where the red fiber optic is. Even when placing the white dot in the notch and using the red fiber optic as point of aim, at 6 feet distance the impact is only about 1 or 1-1/2 inch low.

When I went to test these points of aim at the range, they held true to my tests with the laser ammo, though of course my groupings weren't as tight with real ammo as they were with the laser ammo, lol. So now I have an aiming point for close in defense and I don't have to squish my head down, as well as far away shooting but needing to squish my head, both using the "iron" sights.

BTW, I highly recommend the Laser Ammo by SureStrike. It takes pistol dry firing practice to a whole new level. And if you change sights on your guns, it allows easy pre-zeroing of your sights to get you on paper before you head out to the range to zero with live ammo.
 

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I like the experimentation, and thanks for sharing! Two questions:

1) what did you use to make the white line on the rear sight?
2) if you switch between the factory rear sight hole and the notch, the notch raises point of impact, right? So does that mean the notch is for a longer range zero, and the original hole is a closer range zero? That's how I've worked it out in my head, but I'm not sure if I have it right. :)
 

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Discussion Starter · #3 · (Edited)
The white line is a piece of white pvc electrical tape cut with an X-acto knife.

The notch does raise the point of impact, but in this case it's actually for closer range zero the way I'm using it. If you imagine looking down the sights of the gun to the target as a straight horizontal line, the barrel of the gun below is angled up slightly. At one inch away from the barrel, the bullet will impact the same distance below your line of sight as the barrel is below the front sight. As you move farther away, the slightly angled up barrel makes the bullet travel in a slight up incline, so that at a certain distance away it will cross your line of sight for point of aim being point of impact (poa/poi). That's where you zero. Depending on how far out you're zeroing for poa/poi, the bullet could continue to travel upward higher than your line of sight, then dip down due to gravity and cross the line of sight a second time, for a second poa/poi, then just continue to drop toward the ground as it goes further.

So if my zero with the hole is at 25 yards, then any distance closer than 25 yards the bullet is going to hit low, since the bullet is still climbing up from when it exited the muzzle. So when I'm shooting closer in than 25 yards, I need to raise my aim so the muzzle is at a steeper incline so the bullet will do the first crossing of the line of sight at a closer in distance, for a closer in first poa/poi.

Now if I miss the target complete and only hit air, that will cause the bullet to travel in a higher arc than a bullet shot using the hole, and that higher arc would cause it to travel farther so that when it starts dropping and crosses the line of sight again, that second poa/poi will be farther away than the second poa/poi using the hole. But the way I'm using it I'm hoping that it will impact the target around the first zero distance instead of going on an arc through the air. People who do very long distance shooting will use the second crossing as their intended zero, and in their use raising the point of aim does equal a longer shot.

This diagram shows how a higher arc equals a closer first poa/poi and a farther second poa/poi than a lower arc.
 
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