Why "HK Style" AR Front Sights Dont Work

[Basement-Gunsmith-Z]

This Is Why Hooded, AKA HK Style front sights don't work. This Only applies to hooded front sights with elevation adjustment, such as the troy hooded buis.

With the hooded style of sight you tend to want to align the circles instead of centering the post in the rear peep sight. Some people say that it doesn't Matter that the front sight isn't centered in the rear sight, it does matter. The attached image will show why.

In the image you will see the two lines. The line that starts in the center of the rear sight and touches the top of the front sight post is where your POA (point of aim) should be, But because your brain naturally wants to align the circles. The actual POA is a relatively straight line forward from the front sight post because you aren't actually aligning the front sight post with the rear aperture. What most people are really doing is aligning the circles and putting the front sight post on the target.

I hope i have done a good job explaining this. I have seen some people try, they just didn't include the reasons why it happens. Yes i know it isn't the best drawing, but i don't have a camera so i had to use an old image.

If you have any questions, or if i didn't explain it as well as i hope please post below and i will answer them or improve my explanation.

The Dot in the rear circle is the center.

 

[Ridge_Runner_5]

Look forward to seeing the image

 

[Basement-Gunsmith-Z]

Oh sorry, i could of sworn i uploaded it.

 

[stubbicatt]

Couple of thoughts. Zero the rifle properly with the ring in a ring, and then the post at 6 0'clock, or, perhaps the BUIS you are examining wasn't made with the thought in mind of ring in ring sight alignment.

On the HK it works! Really.

 

[Basement-Gunsmith-Z]

Couple of thoughts. Zero the rifle properly with the ring in a ring, and then the post at 6 0'clock, or, perhaps the BUIS you are examining wasn't made with the thought in mind of ring in ring sight alignment.

On the HK it works! Really.

On the actual hk sights the front sight is fixed with the post exactly in the middle. It works great this way, but you need a rear sight with windage and elevation adjustments. When the front sight is adjusted for elevation the post isn't in the center of the circle and therefore your aim is off. As shown in my picture when the 2 circles are centered but the post is low or high the point of aim tends to go out in a straight line almost paralel from the barrel.

 

[Crow Hunter]

Same problem on the SCAR.

If the post is centered in the circle, it is really nice. If it is low, it really messes with my brain. (Which isn't hard)

For some reason I was thinking that real HK sights the hood and post relationship was fixed to prevent this from happening.

But I have only shot a MP5, it wasn't and it was already sighted in. Plus, I had the happy switch on "burn through someone else's ammo" , so I wasn't really doing precision aiming.

 

[Marquezj16]

I get your reasoning as to why it might not work, but mine works fine with a 50 yd zero out to 200 yards. I have also shot it out to 260, 300, and 340 with minor adjustment on my hold. Can't explain as to why or how.

 

[Basement-Gunsmith-Z]

I get your reasoning as to why it might not work, but mine works fine with a 50 yd zero out to 200 yards. I have also shot it out to 260, 300, and 340 with minor adjustment on my hold. Can't explain as to why or how.

Are you using a fixed front sight, or a front sight with adjustable elevation. I have an image attached to my post. in it the front and rear circles are lined up. What happens when you align the 2 circles is the post isn't centered. Most people will just put the post on target without making sure it's centered in the rear aperture. As illustrated in my image the point of aim goes out in a line almost parallel to the barrel from the front sight, instead of on an angle like it would if the post was centered. In my image i have a line for where your point of aim should be, and where it actually is because of aligning circles.

 

[Marquezj16]

I am using the Troy HK style sights with adjustable post for elevation on a AR15 Carbine. I'll have to make a note next time I shoot it as far as how the circles and post are in relation/location when I am shooting. Never thought about it much. Like I said, it works. I aim and shoot and hit the target.

 

[stubbicatt]

I'll take another run at it...

Whether the rear sight of the HK is elevation adjustable or not, really isn't the issue as I see it.

Assuming the front sight only, post in a globe. If the post is centered in the globe, or whether the tip of the post is below or above the center of the circle circumscribed by the front globe sight, the post will subtend X minutes of angle from the theoretical center of the globe. This subtension, as measured in MOA on paper downrange will remain the same, no matter the distance, as it is a static relationship.

Thus if you zero your rifle at, say, 200 meters using the globe centered in the rear aperture, and set the target on the tip of the post, and you raise elevation your standard come-up for 300 meters, say 3.5 moa for a 300 meter zero, and maintain the same relationship between the front globe and rear aperture, and the target on the tip of the post, it will hit to zero.

The relation between the sights, as measured in moa of deflection, will remain the same, irrespective of distance.

Or did I miss something?

 

[Crow Hunter]

Or did I miss something?

I think what he is talking about, and what bothers me about SCAR sights, is that if you have to move the post tip out of the center of the circle to get zeroed, it can throw off your shots.

When I look through the SCAR sights, my mind automatically aligns the front hood with the rear aperture. This would be great if that happened to correspond with the correct zero. However, at least on my brother's SCAR 16, to get it zeroed at 50 yards, the front post tip is noticeably lower in the hood. If I use the front post tip centered in the rear sight, I am dead on. If I go off my 1st instinct and "circle the circle" I hit really low on the target. I don't do this on standard AR sights because the front sight is an open "U", I automatically put the post tip in the center of the circle since there is no other circle to align that my brain likes better than a circle and post.

There may be a way to bring the rear sight up without changing the BDC and then re-centering the front sight post in the hood, but I don't know for sure and he gets mad if I take his rifles apart.

 

[Basement-Gunsmith-Z]

I'll take another run at it...

Whether the rear sight of the HK is elevation adjustable or not, really isn't the issue as I see it.

Assuming the front sight only, post in a globe. If the post is centered in the globe, or whether the tip of the post is below or above the center of the circle circumscribed by the front globe sight, the post will subtend X minutes of angle from the theoretical center of the globe. This subtension, as measured in MOA on paper downrange will remain the same, no matter the distance, as it is a static relationship.

Thus if you zero your rifle at, say, 200 meters using the globe centered in the rear aperture, and set the target on the tip of the post, and you raise elevation your standard come-up for 300 meters, say 3.5 moa for a 300 meter zero, and maintain the same relationship between the front globe and rear aperture, and the target on the tip of the post, it will hit to zero.

The relation between the sights, as measured in moa of deflection, will remain the same, irrespective of distance.

Or did I miss something?

It's hard to explain, but If you center the circle within a circle without the post being in the center on both the x and the y axis it will be off. If you look at my drawing it will show why. Without the tip of the front sight post being centered in the rear aperture The line of aim runs ALMOST parallel to the bore. Most people using this type of sight will shoot low. at 50 yards when i aligned the circles i shot about 5" low, and no matter how much i adjusted elevation it still shot about that low. It's quite difficult to explain.

I made another diagram, this time in paint. The 2 circles are the front sight hood, and the rear aperture. The red line is the actual line of aim and the green line where the line of aim should be.

Im quite talented at making images in paint, can you tell

 

[sigcurious]

What, if any, HK style AR front sights compensate for the circle/circle post issue, allowing the post to be centered along with the circles aligned?

 

[emcon5]

I think this is what you are trying to convey:

Upper left photo, front post centered in front sight hood, centered in aperture. Ideal.

Upper right, post not centered in front hood, this would be the correct sight picture.

Bottom, post not centered in front hood, circles lined up, but not front post is not centered, so shots will be low.

I expect this problem could be more or less apparent depending on how good your eyes are.

 

[Basement-Gunsmith-Z]

There aren't any hk style front sights that are elevation adjustable that compensate for this issue. If you want accurate hk style buis for your ar you need to get something a rear buis with elevation and windage adjustments like This one and you can just use a hk style front sight, but try to center the post in the circle. And when you need to adjust elevation adjust it on your rear sight.

 

[Basement-Gunsmith-Z]

Thank you emcon. That's one of the things i was trying to show, in my image i also was showing how if the post isn't centered your line of aim goes almost straight out from your front sight and not on the angle downward you would get If the post was centered in rear the aperture.

 

[sigcurious]

Making sure I understand, in emocon5's picture the POI for the bottom center image would be at the top of the post? or would it be elsewhere?

 

[Basement-Gunsmith-Z]

Making sure I understand, in emocon5's picture the POI for the bottom center image would be at the top of the post? or would it be elsewhere?

No the POI won't be at the top of the post. It would most likely be about 5" low at 100 yards. Did you look at my 2 images? I show why if the post isn't centered your point of impact and point of aim won't match no matter how much you adjust your front sight for elevation. If you adjusted the front sight to bring the POI up you would have to center the front sight post in the center of the rear aperture as shown in emcon's top right image.

 

[stubbicatt]

Regardless of where the post is in the ring, I still think that if the rifle is zeroed with that sight picture/sight alignment, it will remain zeroed as you walk thru the elevation scale.

I know this as when I used to shoot free pistol with contact lenses, each time I put those lenses in my eye, it would affect windage. I would go to the range and have to slide the sight right or left quite a few clicks. But once set up, it was perfect the whole day.

Same for using simple aperture and post sights. I have used those different sights in BPCR. The rear is a vernier scale for elevation, the front is a "globe" sight with different inserts. Some are simple post, some a post and ball, there's a crosshair front sight insert and others as well. With the simple post, the top edge of the post was nearly centered in the front ring, but with the post and ball, the ball was definitely above the center point of the front ring. Shot that thing in silhouette tournaments for several years and had no issue having to change come ups using the same load.

Even if the post were above center or below center, with the ring in a ring and the post under the target, once adjusted for this sight picture, you still have a zero that is repeatable at any distance, taking into account changes in the elevation dope on the rear sight. If the post is displaced left or right of the centerline of the bore, you will have windage shift with changes in distance.

I feel comfortable the the OP concerns are not valid, based on my experience.