Just wondering the pros and cons of tube diameter. Vortex uses 30mm on their top of line AMG, 34mm on the gen 2 Razor and 35mm on the Razor HD. I know smaller isn't better or we would all still be using 1" tubes but this mix of different diameter tubes confuses me.
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Rifle Scopes Tube Diameter
- Thread starter 03psd
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More travel from larger tubes. 34mm is pretty much standard on high end scopes now a days. I believe they redesigned the erector assembly on the AMG so they can get the travel out of it.
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In a very basic explanation, more tube diameter means more room to allow for internal travel, which is a plus. The general downside is obvious, more weight. The reason the amg is 30mm is weight was a big concern for Vortex when designing it, where as the gen II it wasn't. There are a lot of other little variables associated with tube diameter, but I'm no expert on them. Extreme range of turret adjustment and weight, as well as ring options (for odd diameters like 35 or 40), are the main things to consider when comparing different tube diameter scopes. As for comparing the different razors, the amg has slightly less internal travel, but offers considerable weight savings over the gen II.
There are other important reasons for larger diameter tubes than just extra movement possible.
The rigidity of the tube increases as the cube of the change in diameter for a given wall thickness while the weight is only increased by the change in diameter. Rigidity of the tube is important to the life of the scope insofar as the mounting of the internal components is concerned. Minor savings in weight are negated by larger glass components but overall, the larger tube is likely to perform better.
Of course, on a hunting gun that is going to be packed over rough terrain, ounces become pounds and every ounce counts. On a square range of the one way type, who cares, you only have to get from the car to the firing line.
The rigidity of the tube increases as the cube of the change in diameter for a given wall thickness while the weight is only increased by the change in diameter. Rigidity of the tube is important to the life of the scope insofar as the mounting of the internal components is concerned. Minor savings in weight are negated by larger glass components but overall, the larger tube is likely to perform better.
Of course, on a hunting gun that is going to be packed over rough terrain, ounces become pounds and every ounce counts. On a square range of the one way type, who cares, you only have to get from the car to the firing line.
For the most part, the larger tubes are there to allow for greater elevation and windage travel, but they do have other pros and cons as already mentioned. None of these are absolute. There are just design tradeoffs.
To add a few other other considerations:
-In high erector ratio riflescopes, extra space due to a larger tube is quite helpful Many of these designs have telescoping assemblies with one sliding inside the other when you adjust magnification. It is easier to maintain durability with complicated optomechanical designs in larger tubes.
-While a larger diameter tube is indeed stiffer for the same wall thickness, it is also more susceptible to deformation (dents) due to incorrect mounting or impact.
-With a larger tube, there is a little more leeway in terms of what kinds of optical components you use. It is easier to optimize an optical design when you have more space.
-You have a little more space to mount larger diameter turrets which often helps with adjustment feel.
Personally, I have never choisen or discarded a scope because of a tube diameter, unless it is something so exotic that I can not find mounts for it. For the three most common diameters (1", 30mm and 34mm), mount availability is not really an issue.
There are a few options for 35mm as well. For 26mm (some old scopes), 36mm and 40mm, it gets a little more involved.
To address something from the original post: smaller is not better, but not necessarily worse either. It can go either way depending on what you are looking for.
With Vortex Razor Gen II vs AMG, the big difference is the weight and the erector ratio. Gen II is a 6x erector ratio, while AMG is a 4x. Shoving a 6x erector ratio scope into a 30mm tube while maintaining appropriate elevation travel and durability is a little bit difficult (though not impossible) which is why most scopes like this have 34mm tubes.
Here is a pretty good way to think about it: there are two possible reticle planes inside a riflescope. Think of a first reticle plane as between the objective and the erector. The second one is between the erector and the eyepiece.
The objective forms an image and superimposes it onto the reticle in the first reticle plane. Then, the erector optical system magnifies that image by whatever the erector ratio happens to be and forms that magnified image in the second reticle plane. That is what you see through the eyepiece.
The image in the second reticle plane has to be six times bigger than in the first reticle plane and you need space to accomodate all of that.
Now, this is a fairly gross oversimplification of the problem, but at least it should give you a reasonable idea.
ILya
To add a few other other considerations:
-In high erector ratio riflescopes, extra space due to a larger tube is quite helpful Many of these designs have telescoping assemblies with one sliding inside the other when you adjust magnification. It is easier to maintain durability with complicated optomechanical designs in larger tubes.
-While a larger diameter tube is indeed stiffer for the same wall thickness, it is also more susceptible to deformation (dents) due to incorrect mounting or impact.
-With a larger tube, there is a little more leeway in terms of what kinds of optical components you use. It is easier to optimize an optical design when you have more space.
-You have a little more space to mount larger diameter turrets which often helps with adjustment feel.
Personally, I have never choisen or discarded a scope because of a tube diameter, unless it is something so exotic that I can not find mounts for it. For the three most common diameters (1", 30mm and 34mm), mount availability is not really an issue.
There are a few options for 35mm as well. For 26mm (some old scopes), 36mm and 40mm, it gets a little more involved.
To address something from the original post: smaller is not better, but not necessarily worse either. It can go either way depending on what you are looking for.
With Vortex Razor Gen II vs AMG, the big difference is the weight and the erector ratio. Gen II is a 6x erector ratio, while AMG is a 4x. Shoving a 6x erector ratio scope into a 30mm tube while maintaining appropriate elevation travel and durability is a little bit difficult (though not impossible) which is why most scopes like this have 34mm tubes.
Here is a pretty good way to think about it: there are two possible reticle planes inside a riflescope. Think of a first reticle plane as between the objective and the erector. The second one is between the erector and the eyepiece.
The objective forms an image and superimposes it onto the reticle in the first reticle plane. Then, the erector optical system magnifies that image by whatever the erector ratio happens to be and forms that magnified image in the second reticle plane. That is what you see through the eyepiece.
The image in the second reticle plane has to be six times bigger than in the first reticle plane and you need space to accomodate all of that.
Now, this is a fairly gross oversimplification of the problem, but at least it should give you a reasonable idea.
ILya
Pulling up this older thread I just now found, searching for an answer to a question I have about tube diameter.
I think I got my answer but I'll ask another way . . .
A larger tube diameter does not by itself give you better field of view, or more light, correct?
The larger diameter is all about adjustment travel and power variability, right?
I think I got my answer but I'll ask another way . . .
A larger tube diameter does not by itself give you better field of view, or more light, correct?
The larger diameter is all about adjustment travel and power variability, right?
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Let's be careful when going from 30 to 34 mm. For many scopes that does not mean the inner diameter increase by 4mm thus yielding more adjustment space, it just means the wall is 2mm thicker. This is true of March scopes and I believe some Nightforce scopes, especially those that are claimed to have thicker walls, and probably may other scopes as well. I believe that going to 40mm is where you get the thicker walls and the additional adjustment space, but I could be wrong.
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