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The Anatomy & Parts of a Rifle Scope: A Complete Breakdown

Parts of a Rifle Scope

When I was a newbie to the optics world, I thought I didn’t have to learn all the parts of a scope.

I thought it was aim and shoot every time, which probably explains why I was so bad back then.

If you’re worried about choosing the wrong scope, then this article is here to save you.

I’m here to give you a complete guide of the rifle scope anatomy to help you understand the basic components of rifle scopes and why you should buy it.

The American Sniper was right when he said: “A marksman’s best friend is their scope”- Chris Kyle

The External Parts of a Rifle Scope:

Diagram of the external parts of a rifle scope

1. Objective Lens

RULE #1 of Hunting: Keep your eyes on the prey.

The objective lens is the furthest away from your eye, and like any other scope, it’s there to transmit light back to the eyepiece (more on this later).

Objective lenses come in diameter sizes ranging from 20-60 millimeters. The general principle is that the LARGER the lens, the MORE light gathered.

I personally like having an objective lens of around 40-50mm as my go-to.

However, having a clearer image comes with the price of making your rifle heavier.

So how does one determine the size?

For example, let’s take the Leupold VX Freedom 3-9x40mm Rifle Scope:

  • The 3-9x helps determine how much you can adjust magnification power.
  • The 44 measures the diameter of the objective lens.

NOTE: Most hunters prefer a lower magnification lens power and a larger objective lens because they give a brighter image of the target.

2. Objective Bell

The objective bell (A.K.A windage bell) holds the objective lenses of any rifle scope. This part of the scope tube continuously increases till the diameter of the objective lens.

Rifle scopes with larger objective lenses have grooves on their objective bell to accommodate light transmission.

In essence, it is the house that objective lenses live in.

3. Scope Tubes (Main Body)

The scope body is a metal tube that holds and connects the ocular lens and the larger objective lens.

This is where you attach scope rings to mount scopes to a rifle. Scope tubes come in three sizes:

  • 1 inch
  • 30mm
  • 34mm

The bigger the scope tube, the heavier it is, so it wouldn’t make sense to have a heavy scope on a lightweight rifle.

SIDE NOTE: Scope tube size = Scope rings size

4. Adjustment Turrets

Commonly found in the main body of the scope are two adjustment knobs for windage and elevation.

Both of these “target turrets” are used to MATCH the scope’s reticle to the aiming point of the rifle for more accuracy.

These turrets allow for external adjustment, so you can freely tweak your rifle scope according to your environment.

IMPORTANT NOTE: Not all rifle scopes can be adjusted by hand.

Some require a coin or a screwdriver. I talk more about adjusting rifle scopes if you’re interested to learn more.

Windage Turret

The windage turret of rifle scopes is located on the right-hand side.

The windage adjustment turret controls bullet impact horizontally (left to right) when zeroing down the scope.

Elevation Turret

The elevation turret is just like the windage turret, but elevation adjustments are done on the top portion.

This turret allows for VERTICAL (up and down) control over your reticle to adjust for bullet dropping caused by gravity.

Some rifle scopes, like the ones produced by Leupold, have a zero stop feature for their elevation turrets. This allows you to preset your turret settings adjusted back to 0.

Windage and elevation are measured in either minute of angle (MOA) or milliradian (MRAD). These measurements are based on 100 yards.

Depending on how far you are shooting, you might have to adjust more or less.

Parallax Adjustment

Parallax adjustments knobs are useful for long-distance shooting.

Usually, rifle scopes are zeroed at 100 yards, but at longer distances, the reticle and target may appear to be on different focal planes.

You might notice the reticle shift a bit when you slightly move your head.

The parallax adjustment knob helps remedy that misalignment to ensure your reticle and target are on the SAME focal plane, thus increasing your accuracy.

5. Power Ring

Any VARIABLE power scope contains a power ring.

The power ring controls decreasing and increasing magnification allowing you to take a closer look at your target.

For example, I mentioned the Leupold VX Freedom 3-9x40mm Rifle Scope earlier. 

With the power ring, you can change the lower magnification level of 3x to a higher level of 9x.

6. Eye Piece

The eyepiece is what holds the ocular lens in place.

In addition, some eyepieces come with a diopter which gives you the power to adjust for reticle focus.

I suggest that the first thing you do when you get a rifle scope is to alter the eyepiece according to your vision.

7. Ocular Lens

Lastly, the ocular lens is the closest to the shooter’s eye.

Its main purpose is to magnify the light from the focal point (more on this below) and transmit it to your eyes.

Furthermore, the ocular lens is designed to have an “exit pupil” wherein light passes towards your pupils, giving a clear image of the sight picture.

NOTE: Both the objective and ocular lens are (supposed to be) fog proof.

The Internal Structure of a Rifle Scope

To give you a deeper look into the internal components of the rifle scope, I have divided their functions into three parts:

1. Objective Lens Assembly

A rifle scope functions similarly to handgun & shotgun scopes. Their objective lenses are found on the front section of the rifle scope.

Diagram of the internal parts of a rifle scope

The light gathered by the objective lens passes through the objective bell and reaches the ocular lens.


Most rifle scope lenses are coated. Coated lenses have a large impact on both the light-gathering characteristics of the scope.

This is because the coat reduces glare and reflection, making light transmission more efficient.

I always recommend going for fully multi-coated lenses for maximum light transmission and reduced glare.

2. Focus Lens Assembly

The focus lens is the first lens behind the objective lens and is placed right below the elevation adjustment knob.

This lens is either fixed or adjustable depending on whether you have a parallax error rotating ring (more on this later).

FIXED-focus lenses are set to be parallax-free at 100 yards. I find these to be best for shorter-range hunting.

Meanwhile, adjustable focus lenses eliminate parallax by moving it closer or farther from the objective lens. 

These are usually used by professional, long-range snipers.

3. Erector Tube Assembly

The erector tube contains the magnifying lenses and the reticle components.

This is inside a variable power scope body and is controlled by the power ring. Serving the purpose of erecting an upright image (hence the word erector).

Windage and Elevation

A spring system compresses the erector tube against the windage & elevation screws, making it possible to adjust them.

Magnification Lenses

The magnifying lens of multi-power scopes moves within the erector tube.

The magnification lens moves closer to the objective lens to increase magnification. The opposite happens to decrease it.

Reticle (Crosshair)

The reticle sight could be placed in front or behind the magnifying lens:

  • If placed in the former assembly, it would be called the first focal plane reticle (FFP).
  • If placed in the latter, it would be called the second focal plane reticle (SFP). 

Wondering which one is better?

I recommend getting the FFP because the image of the crosshair changes in size proportionally to the magnification.

Compared to the second focal plane reticle (SFP), the crosshair changes size  remains constant during turret adjustments.

FUN FACT: Some rifle scopes, like the Zeiss Conquest V4 3-12×56 rifle scope, guarantee illuminated reticle adjustments, which regulate the brightness of light inside the scope tube.

That was a complete dissection of the rifle scope. Let’s move on to the commonly asked questions.

Frequently Asked Questions

Frequently Asked Questions

How Do Rifle Scopes Work?

Here is a general guideline on how the front and end of the scope work to increase your accuracy:

When you aim at a target, light is gathered at the objective lens. The light then moves to the focus lens.

It then passes through the erector tube, where the image is reversed so that it does not become a reflection.

The ocular assembly receives this light, then the “exit pupil” sends it to your eye creating the image.

NOTE: Do not buy a riflescope without adjustment features or an instruction manual.

Do Most Rifle Scopes Have Parallax Error Adjustment?

Parallax is a displacement in the apparent position of your target.

Parallax error is an issue for long-distance shooting since the crosshair does not stay constant.

To mitigate this, some hunting scopes have a parallax adjustment knob placed on the opposite side of the windage knob.

You would often see this on more popular rifle scope brands and optics.

What Components Make a Scope Expensive?

The components that make scopes expensive are the quality of optical lenses:

  • Ocular lens
  • Objective lens
  • Internal magnification lens

Riflescope manufacturers also incur production costs while making the internal structure and components of a scope durable and shock tolerant.

If you’re ready to look for options, you can take a look at our Guide on Scopes Under $500.


I hope this article helped you fully understand the parts of a rifle scope and how the internal components between the ocular lens & the objective lens work together.

The only thing left to do now is buy a rifle scope and make your dream of being Deadshot from the Suicide Squad a reality.

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