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Discussion in 'Long Range Scopes and Other Optics' started by Nvhunter, Aug 4, 2009.
Is there a difference in performance between a 1" or 30mm scope tube?
1" = 25.4 mm
The difference in size is the area of the objective (2*pi*r*r)
1" diameter = 1013sq mm
30mm dia = 1423 sq mm
Nearly a 50% increase in lens area.
Whether that makes a difference depends on a lot of factors (magnification, hunting situation, shooters age ...)
Lets see if we are talking apples and apples.
The objective, to me, is the firing end lens on the scope. I have decided upon on a 50mm Objective lens for the 7mm STW I am building - Sako 75 with Tapered Dovetail scope mount.
The 1" or 30mm performance question refers to the area where the scope rings will attach. The scope I will purchase will be Leupold VX-3 - 50MM objective lens. I have to decide upon 1" or 30mm where the rings will mount the scope.
I have a Leupold VX-III 4.5X14 40mm Long Range with a 30mm tube mounted on my 30.06 and really like it.
I suppose I will need to determine if lenses are in that ring mount area. Good point on the total lens area. I can see where that would help low light transmission.
Yep, I had a senior moment this morning when I read your post (no sleep etc etc.)
The biggest thing you will typically gain with the larger tube is
1) more adjustment (more windage adjustment when your elevation is at/near it's maximum)
2) A bit stiffer tube.
Got it, Thanks. I'll have to learn about this turret adjustment stuff. Always having shot .30 cal ...Well, there really is no need for me to adjust the sights. Just a bit of Kentucky windage has always put food in the fridge.
However, I am sure moving to a distance capable cartridge (like this 7stw) will surely teach me a thing or two. I am really looking forward to range time with it.gun)
Thanks for the feedback.
Actually, the 30mm tube being stiffer than the 1" tube is a myth for the most part...you will be hard pressed to find a manufacture that would stick by that vcaim. The only measurable difference between a 30mm and 1" tube is a greater range of adjustment.
Actually, I believe it's a fact that mechanically, larger tubes (with same wall thickness) will be stiffer than smaller tubes. If it's a myth, then all the guys building mountain bikes have bought into the myth too.
The 30mm tubs have some advantages over the 1" tubes.
They are stronger due to the diameter of the tube, the lenses inside the tube are larger and
thicker allowing the scopes to be shorter. (Look at the same brand and power and you will
see that they are shorter),
Also as mentioned they can have more turret travel (More MOA).
The objective and ocular lenses are the same size.
J E CUSTOM
I also believe another advantage of the 30mm tube is more light transmission to the ocular piece. The 30mm tube was popular in Europe for many years before finding its way to North America. In Europe, their hunting culture provides for ethical hunting and shooting well before sunrise and well after sunset. Their larger objective scopes allow them to gather more light and the 30mm tube allows them to transmit that light to their eye.
Not trying to start an arguement, but I researched this topic heavily just a few months ago. Yes, typically larger tubes are stonger, but in the case of a scope the difference between 1" and 30 mm is so small that it should not be a decision maker. 30mm tubes, at least Leupold's, use the same internal glass as the 1" tubes. If they used 30mm glass, the would not be able to achieve the extra wind and elev adjustments that make 30mm tubes so poular. Therefor, two identical objective scopes, one 30mm and one 1", have the same light transmission. Where you pick up the better light transmission is through the objective, which is why scopes have evolved from 29-36mm objectives to 40-56 objective.
Don't get me wrong, I'm not saying don't buy a 30mm, I have several and I like them, just buy them for the right reason...increased range of adjustment
I recently compared some scopes side by side i.e. 1" to 30mm, same power and objective size, same maunfacturer. Some brands showed a noticeable difference with the 30mm being brighter to my eyes. Some didn't. I suspect that some manufacturers put better lenses or better coatings in the 30mm scopes because they can sell them for more. In plainer words, their 30mm scopes are their higher end scopes. What have you guy's noticed? Also, I will respectfully disagree with fireroad> I am not an engineer, ( maybe one will chime in ) but disagree on the strength issue on this basses...In archery, the arrows are tested and classified by spline, the given amount of deflection of the tube. You can have two arrows with the same deflection rate but different diameters and wall thicknesses. This is done so that you can go to a lighter weight arrow by going to a larger diameter shaft with a thinner wall and still maintain the same strenght/spline classification. If it is significant in an arrow sized tube, why wouldn't it be significant in a larger tube with the same wall thickness, the 30mm tube compared to the 1" tube. The only way that it wouldn't be significantly stronger is if they used a thinner wall.
dewiseman - You are correct...I believe another OP hit the nail on the head by comparing the tubes to bike frames. For the same weight, a larger thinner walled tube is stronger than a thicker walled smaller diameter tube. My point was that some people purchase a 30mm tube soley because they believe it is stronger when in reality 1. a 1" tube on a good scope is plenty strong enough and 2. the reason behind the 30mm tube design was increased range in adjustments. I would fell bad if somone paid the extra money for a 30mm tube because they thought they needed it for strength alone.
The advantage, with the Leupold, in the 30mm tube over the 1 inch tube is the side focus. The 30mm has side focus and the 1 inch does not.
I think it is a big difference in the overall utility of the optic in hunting situations.
As stated above the lenses in the Leupold are the same in the 1 inch and 30mm so no difference in resolution given the same objective dia.
Use this link to see what really happens to your scope tube and mount under fire. We may not all be shooting a 50BMG but most of us don't use a scope or mounts built this heavy either.
YouTube - high-speed video of scope and barrel flexing on a 50BMG