Optics for Varmints

Lesson 9 of 18 · Module 3, lesson 2

Assumes the Hunting Primer. New here? Start there first.

Your objective

By the end, you'll be able to explain the key scope features — magnification range, reticle type, and parallax adjustment — that make an optic well-suited for varmint hunting at 50–300 yards.

Concept ~8 min

The groundhog is standing in the sun at 175 yards, feeding slowly. Your 9x scope shows a blurry brown blob. You squeeze the trigger anyway. You missed — or worse, you hit poorly. A varmint scope is not a luxury upgrade: the target is the size of a paperback book at 100 yards and shrinks fast after that. You cannot place a precise shot on a target you cannot clearly see.

Quick recall

Quick recall — what is the approximate diameter of a groundhog's vital zone (head and neck region) at 200 yards?

About 8–10 inches — roughly the size of a paper plate About 3–4 inches — roughly the width of the head and neck Under 1 inch — like a bullseye target

Show answer

Not quite: About 8–10 inches — roughly the size of a paper plate — The full body is that wide, but the head-neck zone is much smaller — about 3 inches wide at close range, which subtends less than 1.5 MOA at 200 yards. That's a precise shot.
Correct: About 3–4 inches — roughly the width of the head and neck — Right. A groundhog head is about 3 inches across. At 200 yards that subtends roughly 1.5 MOA. You need a scope that can resolve that target clearly.
Not quite: Under 1 inch — like a bullseye target — A groundhog is not quite that small at 200 yards. The vital zone is about 3 inches across — tight but shootable with the right setup and rest.

Why a deer scope falls short

A typical deer scope is a 3–9x or 4–12x with a fixed parallax setting around 100–150 yards. It is designed to put a clear sight picture on a 20-inch-wide vital zone at 30–80 yards in low light. That is a very different problem from placing a precise first shot on a 3-inch target at 175 yards in noon-day glare.

Three things a deer scope often lacks for varminting:

Enough magnification to see the target clearly and confirm your hold
Adjustable parallax to eliminate aiming error at the varied distances varmint hunting demands
Sufficient optical quality to stay crisp through hours of bright sun — thermal shimmer, mirage, and heat waves are real at varmint distances in summer

None of these are deal-breakers at 50 yards with a well-shot rimfire. But by 150–200 yards they add up fast.

Magnification: how much is enough?

For groundhogs, a practical range is 6–18x variable or 4–16x variable. At the low end (4–6x) you can glass the field and spot chucks at distance. Dialed up to 16–18x, you see the target clearly enough to place your hold on the shoulder or head, and you can watch your hit (or near-miss) without lowering the rifle.

Above 24x, field-of-view gets narrow, mirage magnifies significantly in summer heat, and the image turns shaky from any movement or heartbeat at the rest. More power is not always better for a live-target varmint hunt.

Deep dive MOA at magnification: the practical math

One MOA (minute of angle) equals approximately 1 inch at 100 yards, 2 inches at 200 yards, and 3 inches at 300 yards. A groundhog head is about 3 inches across. At 200 yards that is 1.5 MOA — a dot you can see and hold on, but not one you can guess at. At 18x magnification through a quality scope that 1.5 MOA target fills enough of the field of view to hold precisely. At 9x it’s a fuzz. The magnification you need is whatever makes the target large enough to hold confidently, with a defined hold point — not just a shape.

Reticles: duplex, BDC, and MOA grid

Duplex reticle — thick outer posts that taper to a fine center crosshair. This is the standard deer-scope reticle and it works fine for varmints at a single zeroed distance. You aim at the center dot for your zero range; beyond that you hold over based on feel or a memorized chart. Simple, fast, gets the job done at one distance.

BDC (bullet-drop compensating) reticle — additional hold points below the main crosshair, calibrated (roughly) for specific distances. If the BDC is matched to your cartridge and load, dialing to the 200-yard mark and holding on the center means your bullet arrives on target without mental math. The catch: BDC reticles are calibrated for a specific velocity, so they are only accurate if your load matches the calibration. Verify against an actual ballistic chart for your specific load before trusting any BDC marks in the field.

MOA or MRAD grid (mil-dot) reticle — a grid of precise reference marks at known intervals that allow you to both range a target of known size and dial exact holdover in MOA or milliradians. These are powerful tools but require more study time to use correctly. If you are new to varminting, a duplex or well-matched BDC is a more forgiving starting point.

The why First focal plane (FFP) vs. second focal plane (SFP)

On a first-focal-plane scope, the reticle grows with magnification, so BDC and grid marks are accurate at any power setting. On a second-focal-plane scope (most hunting scopes), the reticle stays the same size — which means BDC marks are only accurate at the one power setting they were designed for (usually maximum). For varminting, where you are constantly adjusting magnification as targets move closer or farther, an FFP scope is more versatile with a grid reticle, but it also tends to cost more. SFP with a duplex or BDC used at the rated power is perfectly workable.

Parallax: the adjustment most beginners skip

Parallax error occurs when the reticle and the target image are not on the same focal plane inside the scope. The result: if your eye shifts even slightly off-center, the crosshair appears to float across the target, and your point of impact moves accordingly. At 50 yards this effect is small. At 200 yards it can be 1–2 inches — enough to miss a groundhog’s head cleanly.

Most deer scopes have a fixed parallax set at 100–150 yards. Varmint hunters see shots anywhere from 40 yards (burrow just inside the tree line) to 300 yards (open field). An adjustable objective (AO) ring on the front bell or a side-focus parallax knob lets you dial the scope in at your actual shooting distance.

How to use it: point at the target at your shooting distance. Shift your eye slightly up and down without moving the rifle. If the crosshair floats on the target, parallax is present — adjust the AO ring or side-focus knob until the crosshair stays glued in place no matter how you move your eye. Now you’re set for that distance.

Glass quality and why it matters here more than on a deer rifle

Deer hunters are usually shooting in low light — dawn and dusk — when good light transmission matters. Varmint hunters are shooting in midday summer sun, often for hours. The issue is not low light: it is heat shimmer and mirage at long range, and edge-to-edge clarity at higher magnification.

Cheap scopes go blurry at the edges at 12x, develop chromatic aberration (color fringing) in bright light, and lose clarity through the distortion of a hot summer air column. A better-quality scope with multi-coated, ED (extra-low dispersion) glass resolves a crisp image through the mirage where a budget scope shows a smear.

You do not need a $2,000 scope to hunt groundhogs. But spending $300–500 on glass instead of $80 genuinely improves your shooting — more so on a varmint rifle than on a deer rifle used once a year at dusk.

Scope mounting — the basics

A scope that shifts zero because of loose rings is worse than no scope. The mounting procedure matters:

Clean, dry base screws. Oil or Loctite on base screws changes torque behavior. Most manufacturers specify dry threads.
Set eye relief before tightening. Shoulder the rifle with your cheek naturally on the stock. Slide the scope forward or backward until you see a full, clear image with no dark ring. Then snug the rings.
Torque rings evenly. Ring cap screws should be tightened in alternating increments — a little front, a little back — so the scope tube seats evenly. Typical ring cap torque is 15–18 inch-pounds (not foot-pounds). Over-torquing distorts the scope tube and can ruin internal adjustments.
Check after first 20 rounds. Rings can settle; re-check torque and zero after the break-in session.

Edge case Why high rings vs. medium rings matter on a varmint rifle

A larger-objective varmint scope (40–50mm front bell) may need higher rings to clear the barrel. But the higher the scope, the more your cheek weld changes from your natural head position — you may need a cheek riser or a raised comb on the stock to maintain consistent eye position at high magnification. Fit the rings to the scope, then fit your cheek weld to the rings, and only then confirm zero. A scope that requires you to crane your neck produces inconsistent eye alignment and wandering shots.

Visual anchor: key scope features for varminting

Diagram of a rifle scope showing the objective bell at the front, the main tube with side-focus parallax knob, elevation and windage turrets at the center, and the eyepiece with power ring at the rear. Each feature is labeled. — Diagram (not a photo). Key parts of a varmint scope: objective bell (size affects light-gathering), parallax adjustment (side-focus shown), turrets (windage/elevation), power ring at the eyepiece. The parallax knob is the one most often ignored — don't skip it.

Lock in the concepts

Knowledge check

You set up on a burrow at an unknown distance — your rangefinder says 185 yards. You have an adjustable-objective (AO) scope. What do you do before settling into your hold?

Dial the AO ring to approximately 185 yards, then check that the crosshair doesn't float when you shift your eye Leave the AO where it is — the factory setting is close enough Dial to maximum magnification so the target is largest

Show answer

Correct: Dial the AO ring to approximately 185 yards, then check that the crosshair doesn't float when you shift your eye — Correct. Set parallax to match the target distance, then verify by shifting your eye — when the crosshair stays planted, you're set. This removes a potential 1–2 inch aiming error at that range.
Not quite: Leave the AO where it is — the factory setting is close enough — Factory parallax is typically set around 100–150 yards. At 185 yards with a small target, unadjusted parallax introduces aiming error. Two seconds to dial it in is worth it.
Not quite: Dial to maximum magnification so the target is largest — High magnification helps you see the target, but it doesn't fix parallax. Address parallax first, then find the magnification that lets you hold precisely without the image shaking.

Knowledge check

A BDC reticle's drop-compensation marks are accurate only when:

Your load's velocity matches the BDC's calibration, and (on SFP scopes) you're at the correct power setting You are using any .22-caliber bullet — BDC marks are universal for the caliber The scope is at any power setting — BDC marks adjust automatically

Show answer

Correct: Your load's velocity matches the BDC's calibration, and (on SFP scopes) you're at the correct power setting — Right. A BDC built for a 3,200 fps .223 load is wrong for a 2,700 fps load at the same distance. Always verify BDC marks against your actual ballistic chart before trusting them in the field.
Not quite: You are using any .22-caliber bullet — BDC marks are universal for the caliber — BDC marks are calibrated for a specific bullet weight and velocity, not just a caliber. A 40-grain .22-250 at 3,900 fps drops very differently from a 55-grain .223 at 3,000 fps. Match load to calibration.
Not quite: The scope is at any power setting — BDC marks adjust automatically — On a second-focal-plane (SFP) scope — the most common type — BDC marks are only correct at the one rated power setting. First-focal-plane scopes adjust as you change power, but most hunting scopes are SFP.

Take it to the range first

Before the season, confirm your scope is doing its job properly.

Scope verification before the first groundhog trip

0/6

Check ring screws are torqued correctly — no scope shift after a couple of shots.
Verify eye relief: shoulder the rifle naturally and confirm full, clear sight picture with no dark ring.
At your planned shooting distance, set parallax and check for crosshair float by shifting your eye.
Shoot a 3-shot group at planned hunting distance to see if your chosen magnification gives you a hold-point you are confident in.
If using a BDC, verify the drop marks against your actual load's ballistic chart at 200+ yards — do not trust them blind. Print a drop chart and tape it to your stock if in doubt.
Safety Wear hearing protection for every shot at the range.

Sources

Varmint scope selection guide: https://www.targettamers.com/best-rifle-scope-for-varmint-hunting/
Scope parallax explained: https://www.targettamers.com/guides/rifle-scope-parallax-adjustments/
Parallax correction and varmint shooting: https://outdoorsmans.com/blogs/rifle-scopes/correcting-and-adjusting-rifle-scope-parallax
Scope mounting torque specs: https://warnescopemounts.com/blog/torque-and-scope-mounts-proper-torque-specs-for-scope-rings/
How to mount a rifle scope (eye relief, rings): https://argalioutdoors.com/advice/complete-guide-mounting-rifle-scope
Varmint hunting scope recommendation (magnification, reticle): https://www.vectoroptics.com/Academy/Varmint-Hunting-Scope-Recommendation.html
Riflescope selection for varmint shooting: https://insidefirearms.com/uncategorized/choosing-a-riflescope-for-varmint-shooting/

If you remember nothing else

Varmint targets are small: a groundhog's head is about 3 inches across — at 200 yards that's under 1.5 MOA, which demands higher magnification than a deer scope.
Variable magnification (6–18x or 4–16x) lets you glass at lower power and confirm the shot at higher power without switching optics.
Adjustable parallax (AO ring or side-focus knob) is essential for varminting — fixed-parallax scopes are set for 150 yards and can introduce aiming error at close or long ranges.
Duplex reticles work; BDC or MOA-grid reticles add a second-hold point for known distances and are worth learning.
Glass quality — lens coatings, edge-to-edge clarity — matters more on a varmint scope than a deer scope because you spend hours glassing through it in bright summer light.

How ready do you feel?

How ready are you to walk into a gun shop, describe your typical shooting distances, and come out with a scope that is genuinely fit for the job?

Before you go — a quick look back

Distributed practice: one fast recall from an earlier lesson keeps it from fading.

Quick recall

From Rimfire vs. Varmint Centerfire — at what distance does a .22 LR become unreliable as a groundhog cartridge, and why?

Show me the answer

Show answer

Correct: Show me the answer — Beyond about 75 yards. The bullet drops steeply (more than 5 inches at 100 yards zeroed at 50), retains under 100 foot-pounds of energy, and is very sensitive to wind. The scope you put on the rifle should match the rifle's honest range — no point buying a 6–24x for a .22 LR burrow rifle.

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