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Thread: Centra or Gehmann ?

  1. #1
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    Centra or Gehmann ?

    Hi folks, I'm going to buy myself a new rear iris for my Walther LGM2 and have been looking at the Gehman 565 with adj. Iris, colour filters and polarisers, and the Centra standard 3.0 Combi, which is very similarin spec and price.

    my question is... which is the better piece of kit ?

    cheers in advance.

  2. #2
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    I have to ask the question why? You have a 10m target rifle and you intend to fit a 50m cartridge rifle rearsight iris to it. I would suggest that you are over-specifying to meet the likely requirements. Unless you are shooting competitively outdoors the majority of the time you just do not need all the features that these iris\filter units offer.

    If it were me, the first thing I would do is ditch the polariser, it's surprising how many people have one and rarely touch it. You do need good consistent aperture adjustment, you won't move it much but you do need it function properly when you do. The next thing is the choice of filters, yellow is a must and possibly the orange or peach ones. They tend to increase contrast which is always good. Greys reduce glare and being able to quickly flick through the filters at 50m as the light changes is when you want them. Is that what you require?

    If you are going to shoot indoors, it is a 10m rifle after all, and you really believe that something other than a basic adjustable aperture will improve your performance, then you might like to consider the Centra 1.8 Indoor Iris.

    Hope this gives you something to think about,

    Rutty

  3. #3
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    Hello mate, I shoot outdoors in open fields and enclosed woodland, simply because it makes a change to shooting scoped guns and its more challenging. The distances vary between 10m and 50m, though I'd like to push the rifle to its absolute limits and will probably push the distances out to 75m or so. Just because I can and to see how it performs. Its purely for the challenge and I use shoot n see targets to see how the groups are stacking up.

    I was looking at the 565 as a way of covering all bases without spending an absolute fortune, but as you've mentioned that I wont need the polarisers, I'm thinking I might be better off with maybe a Gehmann 566, which is simply the adjustable iris and filters, which are yellow, green, brown, lt grey, dk grey and orange and offers a filter free option too.

    That said there is only £30 difference betwen the two, which is why I thought maybe go for the 565 and have the polarisers for those just in case moments.

    Or would the polarier option simply be a waste of cash ?

    Also, is there any reason to buy either Gehmann or Centra over each other, or are they pretty much the same quality ?

    cheers

    Ian

  4. #4
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    Hi Ian,

    Given that the LGM2 is a .177 6 ft\lb target air rifle, optimised for 10m standing, I really cannot see that spending £120+ on a rear sight iris is going to make any appreciable difference to the outcome. There are so many variables in the situation you describe that sighting errors due to discrimination are well down the list. The biggest sighting issue you face is selection of the appropriate foresight element for the conditions, given that you are probably using non-proportional targets, i.e. aiming mark size does not vary to provide the same sight picture at each range. I wouldn't go much further than sticking a cardboard tube protruding about 2.5cm in the foresight in bright conditions. This will help maintain a clear and glare free picture. Beyond that I would advise you to save your money.

    All the kit you are looking at is intended for use on target rifles costing £2k - Sky's the limit! You are going to be using them in well defined circumstances so spending another £150-200 on sight accessories to attempt to mitigate the effect of conditions makes sense. But with what you have described, I just cannot see that you are going to achieve any tangible benefit.

    Rutty

  5. #5
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    Hello mate, cheers for taking the time here, I'm hearing what you are saying about simply running with the standard iris, whilst you mention that the area where I perhaps could benefit the most is in the foresight. I understand extending the tunnel to reduce glare will help but I'm wondering what effect an adjustable foresight would have, something like the Centra Duo Glass, would the ability to vary the foresight centre ring help in varying conditions, ranges and with different size targets?

    cheers

    Ian

  6. #6
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    Hi Ian,

    Much of what I wrote in relation to the rearsight accessories applies equally to the foresight. I see some very expensive devices on the end of barrels but when you ask the shooter when and how often they use it, the answer is usually "not a lot". Don't get me wrong, having the best possible clarity for the foresight is important and outdoors this is usually achievable with a sensible combination of rearsight aperture size; should be in the range 1.0 -1.2 mm; (there are sound optical reasons for that) and a nice bold foresight ring. There was a fashion years ago for very thin rings, but as a very experience international shot said to me "When you look through the sights you need to be able to see the foresight, not have to firkle about for it!" The other advantage of a thick ring is that it holds your attention much better and discourages you from focussing on the aiming mark. You need to watch the bit that's moving and that's the end of the barrel.

    Selection of inner ring diameter is a little more difficult, the guiding principles are that all movement must be contained within the foresight and whilst having too small an aperture is detrimental, having too large one is much less so. What you need is good separation between the aiming mark and the foresight ring, don't fall into the trap of having a tight fit as it improves aiming accuracy, it doesn't. Small separation encourages the eye to lose that all important focus on the foresight.

    If you want to try something then have a look at the Centra High End Glass Element. Get the 1.4mm ring thickness. they are £18.00 each but worth it and at most you would probably only require three of them. Get one to try and work on it by shooting a various aiming mark sizes at the same range. Hint here - if you go to www.SCATT.com and download their software it allows you to print proportional targets. The Centra elements do work, no need to go for the coloured ones.

    ATB
    Rutty

  7. #7
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    Hello mate, its all starting to sink in, tho its a big learning curve. For now I'm gonna buy a couple of the Centra elements and give them a go, Ive spoken to a shooting friend this morning and he knows a guy who might be prepared to loan me a Gehmann 512 which will give the chance to play with rear iris sizes and filters without spending. I'm also going to have a look at the SCATT website, looks interesting.

    Thanks for taking time to pass on some knowledge, its helped a lot.

    Regwrds

    Ian.

  8. #8
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    Beretta303,

    I use the Anschutz 9775, the Centra 3.0 & 1.8 Basic, and the 510 Gehmann Basic on my Gehmann Compact 590 rear-sighted rifles.

    I suspect that at least some of these irises are made by the same chappies

    I have found all of these irises to be quite excellent, and use two (2) of the rifles (recoiling springers) for field use, matched with the Centra High End 3mm post element.

    I have felt no need to have any colour filters or polarisers in the rear iris - they can be added to the anti-tube in the rear-sight if needed, and this results in a much simpler and less complex iris.

    It should be noted that these irises have taken the battering from 11 ft.lb rifles in their stride

    +1 on the Centra High End foresight elements - for me, they are excellent performers ( I prefer the 4.6 / 1.2 elements for 10m shooting ).

    Have fun & a good Sunday

    Best regards

    Russ

  9. #9
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    Quote Originally Posted by PhatMan View Post
    Beretta303,

    I use the Anschutz 9775, the Centra 3.0 & 1.8 Basic, and the 510 Gehmann Basic on my Gehmann Compact 590 rear-sighted rifles.

    I suspect that at least some of these irises are made by the same chappies

    I have found all of these irises to be quite excellent, and use two (2) of the rifles (recoiling springers) for field use, matched with the Centra High End 3mm post element.

    I have felt no need to have any colour filters or polarisers in the rear iris - they can be added to the anti-tube in the rear-sight if needed, and this results in a much simpler and less complex iris.

    It should be noted that these irises have taken the battering from 11 ft.lb rifles in their stride

    +1 on the Centra High End foresight elements - for me, they are excellent performers ( I prefer the 4.6 / 1.2 elements for 10m shooting ).

    Have fun & a good Sunday

    Best regards

    Russ
    Hiya mate, cheers for the info, it helps to know that whatever I choose to buy from either maker will do the do in terms of quality.

    Tho its all far more complex than I anticipated, but interesting at the same time and I love experimenting so its all good fun.

    Regards

    Ian

  10. #10
    tufty is offline I wondered how that worked..
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    Hi Ian,

    A polariser is really only useful if you shoot in conditions where there is mirage,this appears in your spotting scope as a boiling effect as air rises on wet ground,the effect this has on the target is that it appears higher than it actually is so the shot goes high,a polariser negates this effect to some extent,it usually only occurs on open ground in sun
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  11. #11
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    Quote Originally Posted by tufty View Post
    Hi Ian,

    A polariser is really only useful if you shoot in conditions where there is mirage,this appears in your spotting scope as a boiling effect as air rises on wet ground,the effect this has on the target is that it appears higher than it actually is so the shot goes high,a polariser negates this effect to some extent,it usually only occurs on open ground in sun
    All a polariser does is reduce glare and improve contrast, it can do nothing to change the degree of apparent target movement caused by refraction (mirage). If you think about it, all you are doing is to alter what is perceived by the eye, you can do nothing to affect the conditions between sight and target that give rise to refraction. What you might achieve with a polariser is to reduce the apparent elongation of the aiming mark by virtue of the reduction on glare but you can do nothing about the refraction that occurs in the cylinder of air between you and the target. If anyone tells you differently, ask them to explain the physics that underpin their answer.


    Rutty

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