Got into a discussion with a friend today who's a Marine and current firearms instructor for a federal agency.  We were talking about sight picture and I was describing to him my MI HK-style front sight.  It's the flip up where the "ears" form a circle instead of flaring out like traditional front sights.

My feeling is that the circle in a circle sight picture this creates is great.  When I'm almost nose to charging handle, centering the front circle in the circle formed by the rear sight is very easy.  There's a small gap between the two so that it's easy to see if it's off even a little.

He asked if the ears moved with the post when you adjusted it.  When I said they don't, he didn't think it was a good set-up because the front and rear circles are lined up, but the post could wind up high or low.  My feeling was that it didn't matter.  Even if the post was a bit higher relative to the circle, everything would still line up.  His position was that this is no good because it's non-standard.  

Thoughts?

I have both and like them both.  I thinks it's personal preference.

Sort of related but concerning the HK rear sight (drum); that thing looks fragile.  Doesn't look like it could take be dropped on very well versus the M16A2 rear sight

He is correct.  Although I use an HK style front sight, if the FSP is not centered in the circle it is not a good setup.  a real HK style sight uses a fixed front and an elevation adjustable rear.  This way the circle and circle will be true.

It is when you tighten it down.... HK Sight Adjustment

I guess the thing is, I can't see what's actually wrong with it.  

On the bottom right picture, the post does wind up a little north of center, but I can't see where that's actually a problem.  Point of aim and point of impact are lined up.  And it seems easier to me to line up a circle in a circle than to try to just estimate that a lone post is vertically centered in a circle.  

The pictures here are obviously an exaggeration.  If my front post is high or low in the circle, it's not enough that I can actually see it.  Which makes it seem to me like I'm still using the sight picture of post in peep so that if I were to pick up a standard setup, I'd be familiar.

Here's another one.  For the standard setup, my friend was saying that the farther back your eye is from the rear sight (to a point), the better your sight picture is.  The post takes up a larger portion of the peep that way, similar to using a smaller aperture.  I'd never heard that before, but it seems to make sense.  But I've also heard that you want your eye close to the rear sight.

I was taught that the closer your eye is to the apeture the larger your field of view will be (another reason nose on charging handle).  Your eye will automatically center the front sight post.  Thats the speed and accuracy of a apeture sight.  I have never liked the HK sights and have seen many broken and loose HK sights on captured G3 rifles.

CD

ETA:  The rear apeture should be blurred out and focus is on the front sight post.  Not trying to align several things at the same time.  My eyes are getting older now so my vision isn't as sharp as it used to be.  I find the I still shoot accurately remember the fundementals by focusing on the front sight.

i personally dislike the HK-style sights for the exact reason you mention. my eye tends to line up the rear sight coincidental to the front sight *hood*. i end up with my elevation wwwaaaaaaaayyyyyyyyyyy off because the tip of the front sight post is not necessarily at the center of the sight hood.

You haven't accurately drawn the standard sight either.  On each side, there are the curved edges which give another vertical point of reference.



As you can see, it's not just simply a post in the middle.  Those curved edges give reference points for centering.  The image I found online looks to be out of alignment a little.  the front sight needs to move to the left a little.

Doesn't that mean that you adjusted it the same way a traditional sight is set, though?  Like, you set the front post to be correct when vertically centered in the rear aperture without regard for the front hood, but are getting messed up because you naturally center the front hood anyway when actually shooting, right?  If you adjusted it with the front hood aligned, your post would be a bit high (or low) relative to center of the circle, but your point of aim would be correctly on top of it if I'm not mistaken.  



I don't think I agree with this.  I left off the "ears" in my drawing because I was told they're irrelevant to the post in aperture sight picture.  I agree they give horizontal reference, but so does the HK style.  And if you're saying they give vertical reference, it's not a constant one because my post may be higher or lower in relation to the ears than yours.  

I'm not trying to argue for this, just to understand why HK might not be the way to go.  I bought mine because I needed a front folding sight and that's what was available.  If the normal type was in stock at the time, that's what I would have bought because it's what I've used before.  While I only have a couple hundred rounds using the HK style, I've liked it so far.  I'm just trying to get the whole picture (ha) so that I don't get accustomed to something that's not the best answer in the long run.

Is the knock against it that, while lined up correctly with the post, having your point of impact not in the center of your aperture is a problem?

I use the KNS circle with a crosshair post and I know exactly what you mean with the circle in a circle thing.  I agree totally that it helps ME line things up quicker and more precise.  What I like about the KNS is that it adjusts for elevation unlike the "ears"

True HK front sights are non-adjustable for elevation, hence the front sight post is always "centered" in the circle/



Elevation adjustments are made on the rear sight.

So the rear adjusts for both elevation and windage?  That seems like a decent set-up.  Are the adjustments made with the phillips screws there?  If so, are there detents or something to "click" into adjustment or do they just turn?

The center of the drum (looking from the top - I'll have to get another pic) rotates clockwise and counter-clockwise to raise or lower the elevation.  It requires a special tool from HK that runs about $65-75.  I see them on Sturmgewehr from time to time but haven't bought one because my sights are already pretty well dead on.

The Phillips-head screws you see are for windage adjustment.