Understanding Scope Specifications: A Complete Guide

Choosing the right rifle scope can be overwhelming with all the numbers, terms, and specifications. This guide breaks down everything you need to know to make an informed decision. Before diving in, browse our complete selection of rifle scopes to see what’s available.

Magnification Range

What the numbers mean: A scope marked as “3-9×40” means it has 3x to 9x magnification with a 40mm objective lens.

Variable vs. Fixed Power:

Variable scopes (e.g., 3-9x, 1-8x, 4-16x) let you adjust magnification for different distances
Fixed power (e.g., 4x, 10x) have one magnification level but are often lighter and more durable

Choosing the right magnification:

1-4x or 1-6x: Close to medium range, fast target acquisition, perfect for tactical applications or brush hunting
3-9x: The most versatile all-around choice, ideal for most hunting situations
4-12x or 4-16x: Medium to long range hunting and target shooting
6-24x or higher: Long range precision shooting, benchrest, or varmint hunting

Pro Tip: More magnification isn’t always better. Higher magnification narrows your field of view and can make it harder to find targets quickly. It also amplifies movement and mirage.

Objective Lens Diameter

What it is: The front lens diameter measured in millimeters (the “40” in 3-9×40).

How it affects performance:

Larger objective lenses gather more light, improving performance in low-light conditions
Common sizes: 32mm, 40mm, 44mm, 50mm, 56mm

Trade-offs:

Larger objectives are heavier and require higher scope rings
A 40-44mm objective lens provides excellent light gathering for most hunting situations
50mm+ is beneficial for dawn/dusk hunting or long-range applications

Exit Pupil

What it is: The beam of light that exits the scope and enters your eye.

How to calculate it: Objective lens diameter ÷ magnification = exit pupil

Example: 40mm objective at 10x = 4mm exit pupil

Why it matters:

Your eye’s pupil dilates 5-7mm in low light, 2-3mm in bright conditions
An exit pupil of 4-5mm works well for most conditions
Smaller exit pupils (below 3mm) can be harder to use and appear darker

Field of View (FOV)

What it is: The width of the area you can see through the scope, usually measured in feet at 100 yards.

Typical ranges:

Low magnification (1-4x): 100+ feet at 100 yards
Medium magnification (3-9x): 30-40 feet at 100 yards on low power
High magnification (6-24x): 15-20 feet at 100 yards on low power

Why it matters:

Wider FOV makes it easier to find and track moving targets
Critical for close-range shooting and dangerous game hunting
Narrower FOV is acceptable for long-range precision work on stationary targets

Eye Relief

What it is: The distance from the rear lens to your eye where you get a full, clear image.

Typical ranges:

Standard: 3.5-4 inches
Long eye relief: 4-5+ inches
Scout scopes: 9-11 inches

Why it matters:

Adequate eye relief prevents scope bite from recoil (especially important with magnums)
Longer eye relief provides more flexibility in shooting positions
Minimum 3.5 inches recommended for centerfire rifles

Tube Diameter

Common sizes:

1 inch: Traditional standard, lighter weight
30mm: Most common on modern scopes, allows for more adjustment range
34mm: High-end tactical and long-range scopes, maximum adjustment range

Benefits of larger tubes:

More internal adjustment range for elevation and windage
Stronger construction
Slightly better light transmission (minimal difference)

Consideration: You’ll need matching scope rings for your tube diameter. Shop scope mounts and rings.

Adjustment Range & Turret Types

Adjustment measurements:

MOA (Minute of Angle): 1 MOA = approximately 1 inch at 100 yards
Mil (Milliradian): 1 mil = 3.6 inches at 100 yards

Turret styles:

Capped turrets: Protected from accidental adjustment, set and forget, ideal for hunting
Exposed tactical turrets: Quick adjustments for long-range shooting, target turrets
Zero-stop turrets: Return to your zero with confidence

How much adjustment do you need?

Hunting: 40-60 MOA total adjustment usually sufficient
Long-range shooting: 80-100+ MOA for extreme distances

Reticle Types

First Focal Plane (FFP):

Reticle size changes with magnification
Holdover marks remain accurate at any magnification
Preferred for tactical and long-range precision shooting

Second Focal Plane (SFP):

Reticle stays the same size regardless of magnification
Usually easier to see at low magnification
Holdover marks only accurate at one magnification (usually max power)
Most popular for hunting

Common reticle styles:

Duplex/Plex: Simple crosshair, easy to use, great for hunting
BDC (Bullet Drop Compensator): Hash marks for holdover at different ranges
Mil-Dot: Military-style with ranging and holdover capabilities
Christmas Tree: Multiple holdover points for wind and elevation, used in precision shooting

Lens Coatings

Quality levels:

Coated: Single layer on at least one lens surface
Fully Coated: Single layer on all air-to-glass surfaces
Multi-Coated: Multiple layers on at least one surface
Fully Multi-Coated: Multiple layers on all surfaces (best light transmission and clarity)

Benefits: Reduces glare, improves light transmission, enhances image clarity and contrast.

Additional Features to Consider

Parallax Adjustment:

Eliminates reticle shift when your eye moves off-center
Essential for precision shooting beyond 200 yards
Side focus or adjustable objective (AO)

Illuminated Reticles:

Helpful in low-light conditions or against dark backgrounds
Battery-powered, multiple brightness settings
Not necessary for most hunting but useful for tactical applications

Weatherproofing:

Waterproof: Sealed with O-rings, nitrogen or argon purged
Fogproof: Prevents internal fogging from temperature changes
Shockproof: Withstands recoil and impact

Matching Scope to Application

Close-Range Hunting (0-200 yards):

1-4x, 1-6x, or 2-7x magnification
Wide field of view
Simple reticle (duplex)
Second focal plane

All-Around Hunting (0-400 yards):

3-9×40 or 2.5-10×42
Capped turrets
BDC or duplex reticle
Second focal plane

Long-Range Hunting (300-800 yards):

4-16×44 or 5-25×50
Exposed turrets or BDC reticle
Parallax adjustment
Either focal plane works

Tactical/Competition:

4-16x, 5-25x, or 6-24x
First focal plane
Mil or MOA matching turrets and reticle
Exposed turrets with zero stop
Mil-Dot or Christmas tree reticle

Long-Range Precision (600+ yards):

5-25x, 6-24x, or higher
First focal plane
30mm or 34mm tube for maximum adjustment
Tactical turrets with zero stop
High-quality glass with ED (extra-low dispersion) elements

Budget Considerations

Entry Level ($200-$400):

Good for most hunting applications
Reliable glass and construction
May lack some premium features

Mid-Range ($400-$1,000):

Excellent glass quality
More features and better adjustments
Great value for serious shooters

Premium ($1,000-$2,500+):

Top-tier glass with maximum light transmission
Best mechanical reliability
Advanced features and precise adjustments
Worth it for serious long-range or professional use

Final Tips

Match your scope to your rifle and intended use – Don’t over-scope a .22 or under-scope a long-range rifle
Buy quality rings and bases – A great scope on cheap mounts won’t perform well. Shop quality scope mounts
Consider the total system weight – Large scopes can make your rifle front-heavy
Test before buying if possible – Look through scopes in different lighting conditions
Buy once, cry once – A quality scope will outlast multiple rifles

Still Have Questions?

Our team at Arms East is here to help you choose the perfect scope for your needs.

Browse our products:

Contact us:

Phone: +1-561-293-2915
Email: [email protected]

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