Does Scope Tube Size Matter?

In this guide, we answer the question shooters ask a lot, Does Scope Tube Size Matter for your specific target or hunting application?

This paper examines the different firearm scope sizes on the market. The most popular sizes will be delved into and contrasted, plus the Pros and Cons of each.

• Myths of Long Distance Targeting
• Exit Pupil
• 1″ tubes
• 30mm Scope tubes
• 34 & 35mm Scope Tubes
• Pros & Cons

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Does Scope Tube Size Matter?

It is trendy to think you have the biggest and baddest scope on the market. However, with a scope tube, this is not the case.

Most shooters are led to believe a bigger tube lets in more light; it does not. The tube diameter has no effect on the quantity of light reaching the eye through the ocular lens.

Incoming light converges at the front lens and then collimates near the center of the tube. The image then proceeds to the eyepiece.

The size of the tube does not affect image quality. Wider tubes encourage some edge blocking of the image and a wider field of view.

Exit pupil is influenced, but not by much, we will get into that subject.

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Myths

A few scope builders have led us to believe; higher magnification means longer distance targeting.

Every long-distance shooter has heard, “I need at least 25X to reach 1000 yards” if that is your extreme range.

• The truth, long-range shots can be taken with low-magnification optics and smaller scope tubes. Skilled shooters consistently hit 300 to 400 yards with a 1X scope. What this boils down to, bigger is not always better, and skill makes up for a lack of magnification.

A misconception many target shooters believe to be to be fact, “the heavier and thicker a scope tube, the more dependable” In the early days of scope building, the theory was; bulkier was better.

However, rapid advancements of space-age materials have shaped our beliefs.

• There is a tremendous amount of kinetic energy released when a shooter pulls the trigger. The energy passes through the gun, then the rings, and finally into the scope. It has been proven; a lighter scope disperses energy better than bulkier heavier materials. Lighter material disperses energy more effectively.

Shooters have been conditioned to believe; Larger main tubes let in more light, and therefore you have a brighter scope. On the surface, this approach seems a no brainer. However, there is a lot more going on inside of your scope than just light.

• A larger main tube allows for more adjustment travel of the erector assembly. The larger the primary tube of your scope, the more elevation adjustment possible. The erector assembly limits the amount of light that enters the eye and has a powerful influence on image quality.

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Which Size Scope Tube Is Best For You?

The best scope size for a shooter is depended on price, shooting distance, the click adjustment range and low light performance.

Larger tube sizes mean a larger objective and magnification lens, which equates to longer distance shooting.

The most popular large diameter scope is the 34mm.

Exit Pupil

It is tantalizing to speculate; larger scope tubes have substantially larger exit pupils. If this were the case, every shooter would be out buying the largest diameter scope tube on the market.

Our eye would be bathed in a wonderful image of a whitetail, 500 yards down-range.

Calculating exit pupil of your scope is done by dividing the objective lens diameter by the magnification. Take a generous 50mm objective lens and divide it by a 4X magnification setting, and you have a generous 12.5mm exit pupil.

Unfortunately, a fully dilated human eye is only 7mm. All circumstances being equal, lower magnification settings generate a cleaner, more crisp image.

Large exit pupils provide more benefits than merely bathing your eye in bright light. A larger exit pupil gives the shooter greater flexibility to position their eye, in relation to the optical axis. In addition, larger exit pupils help to see in low light better.

Another advantage is eye strain. If your shooting position is not ideal, a large exit pupil gives the shooter more opportunity to move around with the same optical results.

Whether a scope has a large or small exit pupil should only be a part your decision. There are plenty of other considerations.

1″ Scope Tubes

One inch scopes are the most common in the United States, primarily because of lower production costs and the number of accessories available. The one-inch tube has a diameter of 25.4 mm.

The two most popular sizes of scope tubes available in the US, are the one inch and 30mm. Whether one is better than the other is entirely a matter of choice. Neither design is intrinsically better than the other.

Long-distance shooters use a 20 MOA base and rail system because they run out of elevation adjustment with smaller tubes. It is important to understand MOA and how these canted bases affect your accuracy and elevation.

A 20 MOA base has the front of your scope canted down toward the barrel. With any setup, you lose nearly half of the elevation adjustment to the UP side. A canted 20 MOA base gives the shooter back the lost elevation.

Pros:

• Broad availability of accessories
• There are many more 1″ scope offerings than any other size
• A one-inch scope can mount on 30mm rings, but not vice versa

Cons:

• A one-inch scope tube may run out of MOA elevation adjustment at greater distances

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30mm Tube

A 30mm scope is the European adaptation of the one-inch scope, with the difference being the metric system.

A distinct advantage of a 30 mm scope tube is the increased adjustment range over a one-inch tube. The 30mm tube gives the erector assembly more room to travel.

Most 30mm scopes have the same size lenses as a one-inch tube. The farther the distance, the more MOA adjustment a shooter has.

Pros:

• Better suited to longer-ranges because of added internal adjustment room
• The tube is physically stronger, given the same wall density of a one-inch tube
• Greater reticle adjustment

Cons:

• Not interchangeable
• Slightly more expensive than other scopes

Check Out: Best 30mm Scope Rings

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30mm or 1″

What scope should you go with? The answer to this question boils down to the same answer as most of your other equipment; what are your hunting and in what conditions?

Swarovski Optic maintains a staunch belief, the 30mm is just plain better, bigger, and brighter but not by much.

The real advantages a 30mm tube has over the 1″ tube are nominal. As described earlier, the 30mm tube has a larger elevation adjustment range, which provides more efficient long-distance targeting.

A second influence is the construction of the tube itself, which will have a thicker wall and lend itself to being a bit more reliable.

This is great for 6.5 Creedmoor, 224 Valkyrie and other flat trajectory rounds.

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34 VS 35mm Scope Tubes

The 34mm tube is more robust because the greater diameter allows for better windage and elevation adjustment. Some shooters believe the FOV is more generous on a 34mm scope.

However, the jury is still out on this. If the shooter is targeting long-distances, say over 600 yards regularly, the 34mm tube size would serve a purpose.

The noteworthy advantage would be to accommodate a larger objective lens.

Another facet to a larger scope tube is the weight. If the shooter is hiking long days into the woodlands, the extra weight can be a handicap.

However, if the shooter is at a targeting range or sitting in a tree stand, the extra weight should not be a drawback.

Above everything else, the larger tubes offer much needed internal adjustment space.

A larger erector assembly accommodates larger magnification lens and better movement of the reticle. The farther out you shoot, the more a bullet's trajectory will drop.

Having more room for elevation adjustment lets the shooter compensate for this drop.

Leupold gives us this scenario when deciding on a larger tube, “The little-known fact is that it’s the erector system that limits how much light is getting to your eye. It also has a big effect on image quality.

Here’s a scenario that you may have run across – you have two different scopes from two different brands with similar specs.

Both have the same magnification range, maintube diameter, and objective lens size. But brand A has 20 MOA less travel than brand B.

How is that possible?

Well you can’t cheat physics, so instead, some companies decrease the diameter of the erector system, thus providing you with more travel.

Of course, the downside is that this also decrease the amount of light and the quality of the image that’s getting to your eye.”

Also Check Out: Best 34mm Scope Rings

Pros:

• Larger tubes allow for more adjustment travel
• Thicker more reliable tube for durability
• More robust erector assembly means larger lens and a more sophisticated Reticle
• More crosshair adjustment for long-range shooting
• Larger tubes provide for greater FOV, added power, and reticle illumination

Cons:

• Weight can be a hindrance
• Rings and mounting accessories may be in limited supply
• The extra cost will be a factor

Also check Out: Best Long Range Precision Scopes Under $1000

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Conclusion

It seems as though scope builders have no bounds when it comes to the size of their scope tubes. At some point manufacturers must recognize there is going to be a point of diminishing returns.

WE all want to know how far a bullet can travel. Nightforce and Vortex are leading the way in ELR shooting with distances beginning at 2500 yards.

It is not about scope tube size or even magnification, the bottom line, clarity and resolution make those long-range shots.

Adding fuel to the long-distance fire, the record for ELR stands at over 2 ½ miles. A Texas man beat that distance this year with a 3 mile shot.

It took the bullet 14 seconds to hit the mark and the Earth's curve was nearly six feet. Those types of shots are not made with a scope from Walmart and it reportedly took days of calculations to make a shot over 3 miles away.

Again, scope tube size is a consideration within a total setup. It is not the ONLY! thing to consider.

If long-distance shooting is your goal, know each of the components of your setup. It is vital to combine every component into one machine, rather than a bunch of different parts.

There is nothing more exciting than seeing a 1500 yard r greater shot hit the target.

The primary advantage of larger scope tubes is the added space for advanced components like the erector assembly.

Just as the statement from Leupold says, the erector system that limits how much light is getting to your eye. It also has a big effect on image quality.

Know what is important, target and conditions come first.