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Thread: Difference between 1" and 30mm

  1. #1
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    Difference between 1" and 30mm

    I was reading on another somewhat gun related internet forum... where a person asked this very same question. Naturally, he got all sorts of misinformation, followed by arguing as to who was right and who was wrong... then the thread pretty much turned to crap.

    So... here is what I can tell you for sure. The difference between 1" and 30mm tubs is: 4.6mm, any more than that is pretty much a guess.

    So, let's look at some of the common assertions and beliefs about the 1.00" vs. 30mm battle... which, I believe is discussed largely because the 9mm vs. 40SW vs. 45ACP thing is just so old now.

    The adantage to 30mm is that it offers more adjustment for elevation: Well, it can, sure... but there is another tube inside of the 1" or 30mm external tube, as well as the associated adjustment assembly, and in a lot of cases, scope manufacturers use the same "guts" in a 30mm tube as they do in the 1" tubes. So, just because a scope has a 30mm tube, it does not mean it has more adjustment, but the only way one knows what the adjustment range of a particular scope is, is to get that spec for that scope.

    30mm tubes most likely caught on because they were "European" and associated with high quality scopes, or maybe the "more is better" mindset... American scope companies had to ofer 30mm tubes to compete -- but the smart buyer will check to make sure that the only feature of that 30mm tube scope, is not the 30mm tube.

    30mm Tubes are stronger: Well, again... they could be. But just having a larger outside diameter does not assure that a tube is stronger than a smaller diameter tube... Given the number of scope tubes that I have seen break, this one really does not matter that much to me one way or the other.

    30mm Tubes are "brighter": This one needs to be broke down into a couple of catagories...

    1. A 30mm tubes will/won't pass more light than a 1" tube: This one is silly, but people argue it... of course a 30mm tube will "pass more light" -- to put this in the best "Are you smarter than a 5th grader, home science project" just ask yourself this:

    Imagine you have a little solar panel, one of them things you shine a light on and it makes 'lectricity, and you masked it off so that only a 1" hole was uncovered and put it under a light and recorded the voltage produced.

    Now, you do the same thing, but with a 30mm hole... do you think the voltage would be higher? Course it would, there is more surface on the panel exposed to the same light -- therefore, there is more "light" getting through the larger hole.


    Of course that is a silly example, and not at all the type of light transmission that we deal with in a rifle scope... so, lets look at the real answer.

    Yes, a 30mm tube can be brighter than the same scope with a 1" tube... can be, most likely is, if it is an expensive scope because they will use premium optics, coatings and engineering -- optics, glass and coatings aside, the increased room in the 30mm tube allows for the use of larger Field Lenses, Erector Lenses and other optics in the tube. Larger optics can receive and pass more light. But then you start to give up some of the increased adjustment room, doh!

    If the manufacturer does not use larger lenses inside the tube, then there will be no difference between a 1" and 30mm tube as far as "brightness" goes. If the manufacturer (properly) uses larger internal optics, the scope can be brighter... will you be able to see the difference? That depends on the user, the conditions and the scope.

    30mm Tubes are 4.6mm bigger than 1" Tubes: Yes, that's right! That is one of the fo'sures... also, that the 30mm scope will need 30mm rings! Truth is, a great number of scopes with 30mm tubes are just that... a scope with a 30mm tube, but folks buy them and it sounds cool when you post on the internet that you have one... Not saying that 30mm tubes are bad, as I pointed out, they may in fact offer a superior package inside -- or they may not... caveat emptor.

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    I've not followed the 1" v. 30mm debate elsewhere, but there is some great food for thought here. Of course, being in Europe, I'm far more familiar with high-end German 30mm offerings than most of what's on the domestic market back home. In that sense, K.L. rightly observes that, while the actual tube dimensions definitely factor into all of this, a lot of the difference you're likely to see with a Schmidt & Bender, Zeiss, or Swarovski really has to do with the quality of the glass and coatings used.

    To the German mindset, where most optics are tailored to hunting, and most hunting is done at night, a 30mm tube is a given and the real issue has to do with objective lens/bell sizes. Most "Jägers" would consider 50mm the absolute minimum for anything but a drive hunt rifle, with 56mm strongly preferred. Now, this may not have any direct application to AR/M4 uses, but it does underscore the point that light transmission is definitely the name of the game over here.

    Moving back into a tactical arena, consider that the S&B PM II line (which I think we would all agree is a clear contender for best in class) uses a 34mm tube. There are several reasons for this, most of which can be inferred from K.L.'s post, but when the best tactical (if long range) optics on the planet are using 34mm tubes, it does take some of the shine away from the idea that a 1" tube is still a relevant selection for critical-use situations. Again, we're not really talking AR/M4-specific applications here, but clearly the upper end of the market is moving away from the old 1" standard.

    Chief

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    Which companys are known to use 30mm tubes with the proper inernals? Ive been eyeing an Leupold VXR and they use 30mm tubes.
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    Quote Originally Posted by K.L. Davis View Post
    ...and in a lot of cases, scope manufacturers use the same "guts" in a 30mm tube as they do in the 1" tubes. So, just because a scope has a 30mm tube, it does not mean it has more adjustment, but the only way one knows what the adjustment range of a particular scope is, is to get that spec for that scope.
    I've answered the question from the "Yeah, there's a difference -- one is 1" and the other is 30mm...," and how the latter in no way automatically translates into more ROM, couched it terms of the above, and been told GFY. Veeeeeery frustrating.

    Some folks can see the trees AND the forest. The ones you can't talk to only see only one or the other.

    Big things are made up of little things, and a scope and it's mount(s) are a system in their own right. Add gun/caliber, and it's a fantastic recipe for a fight that looks like something out of Looney Tunes, where all you see is a cloud of dust/smoke with a fist, a star, and exclaimation points floating out of the center.
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    Isn't a scopes ability to "gather light" related to its objective lens more than the tube diameter? Once it hits the first lens, it's being reduced, reversed, resized(magnified) and reversed again. Tube diameter, I'd think, is more related to the size of the internal lenses and their quality/size over light transmission. Just a guess from physics class.
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    Related to, yes. Governed by, no. The devil is in the details, and he's a jealous bastard.

    For instance, nothing in the physical realm "gathers" light, except for a black hole, and I for one am not sticking a gravitational singularity in front of my eye... Yes, a great deal of the misunderstandings revolve around terminology; this is an area where words/semantics matter.

    A larger objective allows more light to transmit, though some will be reflected, some refracted, and some absorbed by the material. The light that DOES transmit has the same thing happen with every single layer it passes through, so any light "lost" is usually to being absorbed by the medium through which it transmits. This is where well-made, well-cut, well-polished glass plays more of a role, to my mind, than the size of the tube, once the light is past the objective. The difference between a 1" and 30mm tube, in this regard, is evident only to instrumentation and afficionados, but arguably may be their center of gravity between choosing between the two.

    EDIT: Also, don't forget, a giant part of the "brightness" factor is from the optic subjectively moving your eye closer to what you're observing. Pretty much anything with magnification is going to "brighten" a scene. I think of the other stuff as refining that most basic premise, but that's open to interpretation and off-topic.....
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  7. #7
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    Got it JSantoro, I was just introducing another fold.

    Quality lenses, so I've heard, have more to do with better clarity/brightness.

    Aside from that, I've looked thru some S&B glass, Zeiss, Nightforce and others, but the only time I've seen a difference is in really low quality optics (Nstar, Bushnell, Tasco and such) and that's only because I was switching back and forth at the fun store just to see if there was a difference.

    Besides, if I had a gravitational singularity, I'd start building my Warbird STAT! /nerd alert
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