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Discussion Starter #1
Hi Folks,

I have a very nice HK-91 that shoots 10" high at 100 yards and 15" high at 200 using the 200 yard peep setting. I adjusted the rear sight by squeezing in the spring loaded plungers and rotating clockwise many turns and it still shoots high. I notice that the rear sight mount has a ~1mm gap between the mount and the receiver, which seems to be lacking (i.e., no gap is present) in the other HK-91s I've looked at.

Other than relying soley on optics to get this rifle to shoot POA = POI, any suggestions? I've never had this type of rifle not zeroable before.

Thanks,

Scott
 

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One option (just guessing as can't see the rife) is possible the rear sight base is loose or too high. The hand on (and higher risk ;-) option is to take everything apart and check. I would first I would check to see if the rear sight base has movement with respect to the receiver.

It would be interesting to know what size groups are you getting at 100 yards and if the group centers are moving?

Assuming this is an actual HK rifle (if a clone could be other issues), check the muzzle for damage (i.e. take off the flash hider) and in general check for signs of any barrel damage, bending and/or the barrel having been changed.

How does the front sight assemble look compared to the barrel? Would also check the front sight to see if it looks like it is in the correct location (~ centered in the front ring) and that someone had not put in a shorter front sight.

When shooting, I am assuming you are centering the top of the front sight in the center of the rear apperature. Plus I would try shooting with out placing the rifle directly on anything hard, try instead to hold the rifle in your hand and support your hand. If using a bipod, try holding in your hand instead just to see if there is a difference (should not be but one has to try and rule out the variables).

If nothing is found during the inspection then would:

1st Check with different ammo, in particular something that is nominally NATO specification or at least ~150 grain FMJ

2nd Check where you are hitting with the 300 meter apperature and the "V" sight. Shoot with a nominally clean gun but with a couple rounds through the gun since cleaning. Also use a cool to cold barrel.

3rd I would first run the sight all the way down (and back off one "click") and see if this gets you close enough (i.e. 2 to 3 inches high at a hundred yards).

If this does not help. you can either go direct to an HK Smith or first get another HK91 and a set of calibers or micrometers and measure the height of the rear sights, front sights etc. and compare (most any thing found will still take a good HK gunsmith).

Good Luck and appreciate knowing what you find (if you are near Indiana drop me a e-mail).
 

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I adjusted the rear sight by squeezing in the spring loaded plungers and rotating clockwise many turns and it still shoots high.
Did the sight drum bottom out and stop turning? If it did not then I would guess you did not actuate the plungers enough.
 

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Discussion Starter #4
Thanks for your replies, gentlemen.

The rifle is a tack driver, shoots high, but tight with no windage deflection when I adjust the rear drum. However, when I turn the drum, nothing seems to happen i.e. four complete turns of the drum lower POI only about an inch @ 100 yards, and no more. I did not have it stop turning, it will still turn, but doesn't seem to do anything. It still clicks when I turn it. Perhaps I need the appropriate sight tool? I've been using two small punches to compress the detents/locking mechanism.

Yes, is a real HK-91, 1976 vintage.

Perhaps I can take a picture and post it. I love the rifle, just want my sight to work.

Thanks,

Scott
 

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Discussion Starter #5
Yes, I hold the sights as you describe. The rear sight base is tight, the screw has an oblong washer underneath at the bottom where is attaches and a round locking type washer on top of that.

Scott
 

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Thanks for your replies, gentlemen.

The rifle is a tack driver, shoots high, but tight with no windage deflection when I adjust the rear drum. However, when I turn the drum, nothing seems to happen i.e. four complete turns of the drum lower POI only about an inch @ 100 yards, and no more. I did not have it stop turning, it will still turn, but doesn't seem to do anything. It still clicks when I turn it. Perhaps I need the appropriate sight tool? I've been using two small punches to compress the detents/locking mechanism.

Yes, is a real HK-91, 1976 vintage.

Perhaps I can take a picture and post it. I love the rifle, just want my sight to work.

Thanks,

Scott
If it still clicks you are not doing it right. The drum should turn freely. You did not puch in the pins far enough as they are still catching the drum.
 
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