Scope specs explained

The first number is the range: a 5-25×56 magnifies between five and twenty-five times. The bottom of the range decides what the scope can do up close and how fast it gets on target; the top decides what you can identify at distance. Of the 53 scopes here the lowest top end is the Hawke XB1 1.5-5x32 SR at 5× and the highest is the Nightforce ATACR 7-35x56 F1 at 35×. 10 bottom out at a true 1×, where the image is the same size as the naked eye sees it.

Zoom ratio — the erector ratio — is top divided by bottom. A 3-9× is a 3× ratio; a 1-10× is a 10×. Wide ratios are harder to build and cost money, and at the same price a narrower ratio usually buys better glass and a more forgiving eye box. The widest here is the Vortex Razor HD Gen III 1-10x24 at 10×, the narrowest variable is the Leupold VX-3HD 3.5-10x40 CDS-ZL at 2.9×, and one scope — SWFA SS 10x42 Gen 2 — is fixed power and has no ratio at all.

The long answer to “how much do I need” is its own page: how much magnification do you actually need?

The objective is the front lens, in millimetres — the 56 in 5-25×56. It sets how much light the scope gathers and, with magnification, the size of the beam that reaches your eye. That beam is the exit pupil: objective divided by magnification. A 56 mm objective at 25× puts a 2.2 mm beam in front of your eye; at 5× it is 11 mm, more than any eye can use.

Why it matters: below about 2 mm the image dims and your head has to be exactly in place; above about 7 mm the extra is wasted, because a dark-adapted pupil tops out near 7 mm when you are young and nearer 5 mm past forty. Objectives here run from 24 mm on the Burris RT-6 1-6x24 to 56 mm on the Vortex Venom 5-25x56 FFP, median 42 mm. At top magnification the exit pupils range from 1.6 mm on the Nightforce NX8 4-32x50 F1 to 6.4 mm on the Hawke XB1 1.5-5x32 SR; 9 of the 53 drop under 2 mm at the top of their range, which is the price of a high top end on a modest objective.

Every exit pupil on this site is computed, not measured. Exit pupil and twilight factor are computed from the published magnification and objective diameter, not measured. Real exit pupil is also capped by the erector at low magnification, and coatings and glass quality move low-light performance in ways the formula cannot see — read these as comparisons between layouts, not verdicts on scopes.

Exit pupil says how bright; twilight factor says how much detail. It is the square root of magnification times objective, and it exists because magnification helps you resolve detail in dim light as much as brightness does — which is why a 10×42 reads antlers at dusk better than an 8×56 even though the 8×56 is brighter. Higher is better, and the number climbs with magnification, so it is quoted at the top of the range.

Across the catalog it runs from 12 on the Burris RT-6 1-6x24 to 44.3 on the Nightforce ATACR 7-35x56 F1. It ignores glass and coatings entirely, so treat it as a comparison between layouts: two 5-25×56 scopes have the same twilight factor whatever they cost.

In a first-focal-plane (FFP) scope the reticle sits ahead of the erector and is magnified with the image, so its hash marks subtend the same angle at every power. In a second-focal-plane (SFP) scope the reticle sits behind the erector and stays one size on screen; its marks are correct at one magnification only, almost always the top. Hold over or range with the reticle at any power other than the top, and you want FFP. Dial the turrets, or shoot a low-power hunting scope, and SFP is bolder and cheaper.

28 of the 53 scopes here are FFP and 25 are SFP. 22 of the 28 FFP scopes are illuminated, which is not a coincidence: an FFP reticle at the bottom of its range is thin enough to lose, and the illumination is what keeps it usable. Browse every FFP scope or every SFP scope, or read the full argument.

A duplex is the plain crosshair with thick outer posts, still the default on hunting scopes because it is fast and uncluttered. A BDC (bullet-drop-compensating) reticle adds holdover marks calibrated to a nominal cartridge — right for one load, approximate for the rest. A hash or tree reticle marks the vertical and horizontal in MOA or mils so you can hold any correction; the tree adds wind holds below the centre. The reticle’s unit should match the turrets’ unit, and every scope page here names both.

Illumination lights the centre of the reticle, usually red, in steps. It does nothing for image brightness; it solves a black reticle vanishing against a dark target in the last minutes of light, and it makes an FFP reticle usable at low power. 37 of the 53 scopes here are illuminated. On an LPVO it is close to mandatory, because a daylight-bright dot is what lets you shoot at 1× with both eyes open.

Turrets move the point of impact. The unit is MOA (minutes of angle) or MRAD (milliradians); one mil is 3.438 MOA, one MOA is 1.047″ at 100 yards and one mil is 3.6″. Neither is finer in any way that matters. 28 scopes here are MRAD and 25 are MOA (all MOA, all MRAD). Every travel figure on the site is shown in both units, converted at that ratio.

Click value is how far one click moves impact — ¼ MOA or 0.1 mil are the norms. Elevation travel is the total range the turret can dial, and it is the number that decides how far you can shoot before you run out of adjustment; usable travel is about half of it once you are zeroed, unless the mount is canted. Of the 53 scopes that publish it, travel runs from 40 MOA on the Trijicon Huron 3-9x40 to 180 MOA on the Hawke XB30 Compact 1.5-6x36 SR; 26 have 100 MOA or more.

Exposed turrets are tall, uncapped and meant to be dialed every shot; capped turrets are set at zero and covered. 31 scopes here run exposed turrets. A zero stop is a hard stop at your zero so you can dial back to it by feel in the dark; 31 of the 53 have one. The long version of the unit argument: MOA vs MRAD.

Parallax is what happens when the target image and the reticle are not in the same plane: move your eye behind the scope and the reticle appears to drift across the target. The fix is to focus the target onto the reticle’s plane. Cheaper and lower-power scopes fix that focus at one distance — usually 100 yards for centerfire, 50 for rimfire — and are sharp near it and slightly soft elsewhere. Side focus (or an adjustable objective) lets you set it for the shot, which matters above about 10× and at any distance far from the fixed setting.

26 scopes here have adjustable parallax and 17 are fixed. The closest focus is the SWFA SS 3-15x42 Gen 2 FFP, down to 6.6 yards — close enough for an airgun. A fixed 100-yard scope on a .22 is the classic mismatch; that is the whole reason the rimfire category exists.

The distance from the eyepiece to your eye at which you see the full image, in inches. Too short and heavy recoil brings the scope into your eyebrow; too long and the scope has to be mounted awkwardly far forward. Around 3.5″ is the norm on a rifle scope, and eye relief usually shortens a little at the top of the magnification range, which is why some makers publish it as a range.

Of the 53 scopes that publish it, the shortest minimum is the Trijicon Huron 3-9x40 at 2.5″ and the longest is the Riton 3 Primal 3-9x40 EER at 5″. Read it with the cartridge in mind: the number that is comfortable on a .223 can be a problem on a magnum.

How wide a strip of the world you see, quoted in feet at 100 yards, at the bottom and top of the magnification range. It collapses as magnification rises, which is the practical cost of a high top end: finding a target and following a moving one is harder at 25× than at 5×. European makers publish it in metres at 100 m; multiply by 3 for feet at 100 yards, which is what every figure here is.

At low power the widest here is the Sig Sauer Tango-MSR 1-6x24 SFP at 124.8 ft and the narrowest is the SWFA SS 10x42 Gen 2 at 11.8 ft, of the 53 that publish it. Field of view is also a proxy for eye box: a generous field at the same magnification usually means a more forgiving head position.

The diameter of the tube the rings clamp, in millimetres — or 1 inch, which is 25.4 mm. It does not make the image brighter. What a bigger tube buys is room for the erector to pivot, which is elevation travel, and stiffness. What it costs is weight and a different ring size; 30 and 34 mm rings are everywhere, 35 and 36 mm are not.

In this catalog: 11 on a 1-inch tube, 24 on a 30 mm tube, 17 on a 34 mm tube and 1 on a 35 mm tube. The long version: what tube diameter actually changes.

Weight is the spec hunters underrate and precision shooters ignore. Every ounce on the scope is carried for every mile of the hunt; on a bench it does not matter at all, and the precision scopes here are heavy because travel, a big objective and a 34 mm tube all weigh something. Length matters for mounting: a long scope on a short action can run out of rail.

Of the 53 scopes that publish weight, the lightest is the Hawke XB1 1.5-5x32 SR at 13 oz and the heaviest is the Tract Toric UHD 4.5-30x56 FFP MRAD at 41.5 oz — the median is 22.9 oz. Lengths run from 8.3″ on the Hawke XB1 1.5-5x32 SR to 16″ on the Nightforce ATACR 7-35x56 F1. Published weights sometimes include a throw lever or caps and sometimes do not; where a maker says so, the scope’s page does too.

Scope warranties are unusually generous — several makers will repair or replace a scope for any reason, forever, with no receipt — and that policy is worth real money on an instrument that gets dropped, banged into truck doors and left in the rain. 42 of the 49 scopes here with a stated warranty carry some form of lifetime or unconditional cover. Read the fine print for whether it transfers with the scope.

Country of origin is recorded only where the maker or a retailer states it: of the 9 that do, 6 are from Japan and 3 are from USA. The same brand routinely builds different lines in different countries, so a brand name is not an answer.