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Thread: open sight picture - ZKK 600

  1. #1

    open sight picture - ZKK 600

    Hi ,

    I was just reading up on the use of open sights and to tell the truth I find the correct use of open sights a bit confusing.
    My rifle, being an old BRNO in 270win has fixed open sights that can not be adjusted (contrary to many I see on the internet that can adjust for windage), so I guess they were adjusted at the factory and fixed into place.

    It has a front bead and a back square notch.
    What I find confusing is the sight picture that is recommended for this type of open sight. If we look at the ZKK Owners Manual, on page 27 it shows a picture (figure 8). The image depicts the open sight picture and the top of the bead with the bulls eye of the target sitting on top of the bead. My questions being:

    are all target bulls eyes the same size?
    what distance would this hold true for?
    on an animal at 50m or 100m where would I consider the POI to be in relation to the front bead?

    I had always held the bead centred directly over what I wanted to hit (hiding the POI, like I would with a red dot). Whereas from what I have read I should be holding my POI above the bead!
    I realise many will say go to the range and figure it out, but I have very rare opportunities to do so as the closest range is almost two hours away and extremely expensive. Though I will do so when I get a chance same as I did to zero my sight.
    And anyway I have never been sure of what range the rifles open sights was fixed at, 50, 100, 150 or 200m? and for what projectiles?! Data on the internet is scarce for this rifle as the manufacturer is no longer the same and CZ isnt very good at answering questions about old rifles.

    Does anyone shoot old BRNO's with open sights? Any data would be helpful and probably for other rifles would hold true for mine as well.

    ps. (I currently have an AIMPOINT set up on my rifle and it has been zeroed accordingly for 150gr PPU's. But you never know when one needs to take off the reddot sight and rely on the open sights. Its always useful to know how things work.

    cheers.
    a.
    Last edited by ileso; 07-10-2016 at 14:29.

  2. #2
    I have the same rifle in 7x57 Mauser, just acquired it, like new condition, a few weeks ago.

    I have only shot 140-gr PPU in it one morning at 50 yards, and it shot a tight group, centered up to the sights.

    I am eager to get it out and shoot some other ammunition, and my own handloads, of different weight. American 7x57 ammunition is a bit anemic, because there are so many old military Mausers floating around here. The typical 140-gr load is about 2,650 fps, whereas a safe handload would be about 2,800 fps with ease.

    Then I can see where it shoots at different ranges and what the zero range is for different loadings.

    The sight picture is like one would use on a target handgun. Once you get used to it, it works very well on targets and game, because you are not obscuring the target at close range. At longer range, the bullet strikes right at the top of the square blade or bead. If it is a bead, you can then use a third hold through the center of the bead for yet another, further range.

    The blade can be removed by pushing down a spring-loaded stopper pin in the front of the ramp. Yours may have a set screw. The blade then slides out, so you can change for one of a different height to change the far zero ranges, or change from square blade to round bead. CZ has blades, and so do gunsmiths, like New England Custom Guns here in the USA.

    So what you need to do first is find an accurate load, and use a consistent hold on a bullseye target, starting at 25 or 50 yards. Measure how high the center of the small group is above the bottom of the bull / top of the sight blade. Let's say it is 1 inch and you are shooting 139-gr spritzers at 2,650 fps.

    Now move out to 100 yards, and a larger bullseye, and shoot a good group. Let's say that, for this load, they strike about 1.5 inches high. As you move the target on out, you will find the zero is about 170 yards, as long as you can hold well enough to shoot tight groups. If the bullet is traveling 2,800 fps and is 1 inch high at 50, it will probably be about 2 inches high at 100 and on zero at about 200 - perfect for hunting big game.

    Inside 100 yards, all the standard loads, from 120 grains to 175 grains, should be hitting about the same spot. You won't see much difference in elevation until you pass 150 yards, and it will really become apparent at 200 yards with 175-gr RN and something like a 120-gr at 3,000 fps.

    So you don't need to do much fretting about all that; just find some accurate, inexpensive ammunition that you might use for hunting, and concentrate on those.

    I have three .270 Win rifles with iron sights - one with a Redfield aperture, Remington M700 with open sight U-notch and bead on the front, and a Steyr Mannlicher Stutzen with a square blade, so I can tell you how I have them set and where they strike at various ranges with a variety of loads.

  3. #3
    Yes, my front bead is detachable, though as yet i have not been able to remove it, it has a small button in front of the bead sight. Quite easy to acquire from CZ.

    What is bothering me isnt that so much as what my sight picture should be... because I have to travel about 140km to get to a rifle range as I am not allowed to just go out the back and shoot rounds its not easy for me to test things like this, you guys in the Us have it easy as far as shooting is concerned ....
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    the Brno manual has the following, but i dont see how it should be when in a hunting situation.
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    my target should be above the bead or behind the bead...?
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    apparently either way is used in different situations. if the POI is the point of aim just touching the top of the bead, then how can this hold true for the six o clock position as well?!!

    Maybe i should just place the dot where i want it to go and pray it hits.
    Last edited by ileso; 07-10-2016 at 18:20.

  4. #4
    First off - if you hold your sights with the bead dead on center of the bullseye, at some 25, 50, 100 yards, where do the bullets group?

    Does that center hold sight picture seem more natural to you?

    If so, and it is still shooting above that point, you can replace the front bead with a higher one, to make the rifle shoot lower. But remember, it is only going to be dead on center at one close zero as the bullet rises and other somewhere out there at your hunting zero range.

    ---- now, then...

    Most people who are shooting open sights with a bead want the bullet to strike in the middle of the bead. If the target is a round bullseye, they want to put the bead right in the middle of the target. This would be especially true with an aperture rear sight, as the eye will naturally try to center everything up together.

    But others, who shoot a variety of handguns and rifles with open sights, might want the bullet to strike at the top of a flat front blade, or on top of the bead, for uniformity.

    The most flexibility is what I described earlier, and what Brno shows in their manual, with the target uncovered and resting on top of the front blade or bead, with the bullet striking somewhere between the center of the bead, on top of it, or 2 inches above it, depending on the distance.

    When shooting something like a squirrel, you just sit his head on top of the blade or bead at the closer range. At, say, 75 yards, you hold the bead or top of the front blade dead on his eye.

    When shooting a deer, you have to use your imagination, and visualization, like a archer, to "see" the heart in the deer at 100 yards, and let it rest on top of your front sight. At 200 yards, you hold dead on.

    The rationale for this is that it is easier to judge hold under at closer range than it is to judge hold over at long range, especially if you are obscuring the target with the front sight.

    It works, and was worked out on muzzle loading rifles long ago. It worked for decades before telescopic sights came into common use in the 1960s. Don't try to work it all out in your head. See if you can borrow an air rifle and try it at 10 meters to 30 meters, to get the knack of it, before burning a lot of centerfire ammunition.

    You have to practice and get used to the sight picture until you don't think about it - until you know your rifle at every range. Don't make decisions and changes sitting in your armchair. Go shoot.
    Last edited by Southern; 07-10-2016 at 19:13.

  5. #5
    You have to practice and get used to the sight picture until you don't think about it - until you know your rifle at every range. Don't make decisions and changes sitting in your armchair. Go shoot.
    cheers,

    I will take up your advice and go shoot things to get to know my rifle better. I understand how trajectories work, which is helpful, but got confused when I read different things about the same subject... like when trying to find out what the correct hold on a target should be for example.

    Most people who are shooting open sights with a bead want the bullet to strike in the middle of the bead. If the target is a round bullseye, they want to put the bead right in the middle of the target. This would be especially true with an aperture rear sight, as the eye will naturally try to center everything up together.
    that is exactly how I always thought things worked because I am used to hunting with a SxS that has a brass bead for a sight, where I consider the bead the center of spread. However since I bought my rifle and began shooting with it I transferred that habit into rifle shooting and could never hit what I was aiming at, which made me try to investigate what the factory settings for open sights for the BRNO where... so I ended up buying the AIMPONT (which i dont regret by the way).

    In the back of my mind I am always aware that the sight might one day fail me, at which point I would need to rely on oldschool open sights. So when I began reading up on the subject it all got confusing, because the general consensus is to shoot above the sight, in some place to hit the top of the bead and in others to hit 3/4cms above that (I guess distance is a factor here). Having now slept on it has begun to actually make sense. After all thats how I was used to shooting my air rifle as a kid. I liked the POI to be the top of the flat. So it begins to make perfect sense that with a bead it should be the top of the bead, after all you dont want to obstruct the target with a bead because you lose sight of the target... its not like shooting a load of no.6 at a pigeon...

    so once again, practice, practice practice.
    cheers for the chat, it helped quite a bit.
    Last edited by ileso; 08-10-2016 at 19:55.

  6. #6
    Back to the first post. Do you mean that you cannot adjust the windage at all?? How were the sights attached to the barrel then? I have several iron sighted Husqvarna and Mauser rifles with fixed sights but the windage was adjustable by tapping the rear sight in it's dovetail. Not the case with yours??~Muir

  7. #7
    Quote Originally Posted by Muir View Post
    Back to the first post. Do you mean that you cannot adjust the windage at all?? How were the sights attached to the barrel then? I have several iron sighted Husqvarna and Mauser rifles with fixed sights but the windage was adjustable by tapping the rear sight in it's dovetail. Not the case with yours??~Muir
    well I am going to guess that if I get a hammer out It will move... As you mention its inserted in a dovetail but has been fixed in place in the factory... banging it with a hammer doesnt appear to be a very precise way of adjusting a sight..
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  8. #8
    Your rear sight is exactly like mine. You can see where it was marked as centered up when they regulated it with some load, probably a 175-gr at 2,400+ fps. I have not measured my dovetail, but will do so. It should the the modern standard of 14mm. If you want to change it, you can find sights with two leaves, or one with windage and elevation adjustments. I did that with my Oberndorf Mauser in 8x60S, which was missing its rear sight. I put in the adjustable leaf from the NECG rear sight from a Winchester Model 70 Express .375 H&H - not purist restoration, but works like a charm.

    Once you get the elevation and holds figured out at 25, 50, 100, 150, 200 yards, if you need to shift the windage for your pet load, just tap the rear with a brass hammer and move it about 1/100 of an inch at a time. It is easier to do than you think.

    First thing to do is shoot a tight group at 50 and at 100 to get a close approximation of the MOA elevation setting of your sights. I am doing the same with my 7x57 right now, so I will post what I learn.

    CZ spare parts... open sights
    http://www.cz-spare.parts/rifle-sights/c-1215/
    Last edited by Southern; 09-10-2016 at 01:00.

  9. #9
    Quote Originally Posted by ileso View Post
    well I am going to guess that if I get a hammer out It will move... As you mention its inserted in a dovetail but has been fixed in place in the factory... banging it with a hammer doesnt appear to be a very precise way of adjusting a sight..
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    But, of course, it is. Get a brass faced or nylon faced hammer and give it a brisk tap if necessary. This will defeat the staking they did at the factory. I had to do it with my CZ 527 762x39 and a host of others including my Husqvarna 146 in 9.3x57. I would wait to do this until you find your top accuracy load and get the front sight regulated. For the aforementioned 527 I ordered every front sight insert they had and used the one that had the rounds dropping on top of the bead at 100 yards. Once I had done this I gave the rear sight one rap and it was done.~Muir

  10. #10
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    I always treat a bead sight and notched rearsight as if it were a standard blade siight (Patridge (the inventor's name...not the bird mis-spelt..type) and sit the target on top of the bead. Which if white metal I'll try and black permanently. Then zero such that the bottom of my group touches the top of the bead. So I am shooting "high" just enough to see the bullet strike. I don't see any advantage...and much disadvantage...with having the top of the bead or patridge zeroed so that it aligns with the centre of the group.

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