Tube Diameter

Tube Diameter

So, how important is the tube diameter of your scope when it comes to your target or hunting application? It’s a subject that many hunters and long-range shooters debate, and they often spend far more money than they need.

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Tube diameter of your scope, how important is it when it comes to your target or hunting application? It’s a subject that many hunters and long-range shooters debate, and they often spend far more money than they need. Hopefully the information below helps identify ‘what’s what’.

Tube Diameter

Popular scope tube sizes will be compared in the article below, as well as the benefits and restrictions of each. 

A larger diameter scope tube does enable a marginal increase in the field of view however it does not affect image quality in any significant manner either positively or negatively. 

So with the above mentioned in mind, how does a shooter sift through the BS drilled into the market through clever marketing strategies? Read on, because Hunting in Australia has done some research for you.

So, what tube size is best? The best scope size for a hunter is dependent on price, shooting distance, adjustment range and low light performance.

Into the nitty gritty then:

Exit Pupil

It would be remiss to think that larger scope tubes have significantly larger exit pupils.

Limitations of the human eye unfortunately mean that we cannot take advantage of this diameter.

Find our article dedicated to the Exit Pupil here:

25.4mm Scope Tube (1" Tube)

Due to the lower production costs 25.4mm tubed scopes are the most common in the Aussie market. 

Long-distance shooters would use a positive Minute of Angle (+MOA) rail system because you tend to run out of elevation adjustment with this smaller tube at longer distances.

It is important to understand MOA and how these canted bases affect your accuracy and elevation with your scope of choice.

Read more about Minute of Angle (MOA) here:

+MOA base

What is a +MOA base? A +MOA base lowers the objective lens down toward the barrel. With any setup, you lose nearly half of the elevation adjustment to the UP side. A canted MOA base gives the shooter back that lost elevation.

Note: One minute of angle = 1/60th of a degree

+20 MOA Picatinny Rail
+20 MOA Picatinny Rail

Read more about +MOA scope mounts here:

MOA mounting rail
MOA mounting rail



34mm Scope Tube

The enhanced adjustment range of a 34mm scope tube over a 25.4mm (1″) tube is a noticeable advantage. The erector assembly has greater room to move thanks to the 34mm tube.

Scope Erector Tube Assembly 25.4mm
Scope Erector Tube Assembly 25.4mm

Larger scope tube gives the erector assembly more room for adjustment. Therefore you can take advantage of the space to allow adjustment out to a greater range. Without requiring the assistance of a +MOA or +MRAD rail, which raises the rear of the scope to achieve the same objective. 

Scope Erector Tube Assembly 34mm
Scope Erector Tube Assembly 34mm

Read about the erector assembly here:

Many 34mm scopes share the same lens size as those with a 25.4mm (1″) tube. The more MOA adjustability a shooter has, the longer distance achievable.



34mm or 25.4mm (1")?

Which scope should you choose? The answer to this question is the same as it is for the majority of your other gear: What are you hunting for and under what conditions? There are so many variants on the market to suit all budgets and purposes.

Swarovski Optic (Hunting in Australia believe Swaro’s are market leaders when it comes to glass) is adamant that the 34mm is simply superior, bigger, and brighter, but only by a small margin.

Advantages of a 34mm tube over a 1′′ tube for most hunters are insignificant. The 34mm tube, as previously stated, offers a broader elevation adjustment range, allowing for more efficient long-range targeting. A second factor is the tube’s construction, which will have a thicker wall and be more trustworthy.


When it comes to the size of scope tubes, it appears that scope builders have no limits. Manufacturers must eventually accept that there will come a moment of diminishing returns.

Hunters of today are caught up in light transmission. To a point, they would be correct. The more light that is transitioned to your eye the more you can see. However, an increase in the tube diameter is not going to play a major part in that scenario, that is where your objective lens comes into play.

We’re all curious about the range of a bullet, clarity and sharpness make those long-range shots possible, not scope tube size or magnification.

If long-range shooting is your aim, you should be familiar with all of the components of your setup. It is critical to merge your componentry into a single machine rather than a collection of separate elements.

Your target and conditions should always come first, then you can pull the trigger.

FAQ (Frequently Asked Questions)

No, due to the kinetic energy that travels through your boom stick into the scope rings and subsequently the scope, lighter materials will disperse the energy more efficiently, thus affecting your optic less over shot repetition.

Nope! Many shooters are led to believe that a larger tube allows more light in, this is simply not true in any meaningful quantity. The amount of light that reaches the eye through the ocular lens is largely unaffected by tube diameter. Light converges at the front of the scope through the objective lens before colliding towards the tube’s centre, this is how light enters the scope and subsequently your eye. The benefit of an increased Tube Diameter is restricted to more elevation and windage adjustment thanks to increased travel within the erector assembly. However, a large erector assembly can affect light transmission by a small degree through the tube which can impact image quality.

Tube size can matter at long range because a larger tube will allow more room for the erector tube assembly to adjust for the greater distance. Generally, in everyday hunting, it makes little difference.

The most common tube sizes are 25.4mm (1″), 30mm and 34mm. With the larger diameter tubes being more suited to long-range shooting.

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