Hunting Scopes: Choosing, Mounting and Zeroing the Glass on a Deer Rifle

The scope is the half of a hunting rifle that new buyers get wrong most often, either by spending too little or by buying too much magnification. A hunting scope has to gather light at dawn and dusk, hold zero through a season of truck rides, and let you find a deer in the glass quickly at forty yards as well as at three hundred. This guide covers what those needs mean for magnification, reticles, size and mounting, and how to put a scope on a rifle so it stays put.

Magnification

A three-to-nine power variable has been the standard deer scope for half a century because it fits the hunting: three power to find a deer in timber at close range with both eyes open, nine power to place a shot at three hundred yards. Two-to-ten and three-to-twelve are modern equivalents with a little more reach. Higher magnification narrows the field of view, magnifies your wobble and dims the image at dusk; a fifteen-power scope on a deer rifle is a target scope on the wrong gun. For thick timber and lever guns a one-to-four or two-to-seven is ideal, and for open western country a four-to-sixteen earns its keep. Leave the scope at its lowest power while walking and turn it up only for the shot.

Objective size and light

A forty-millimetre objective lens is the sweet spot on a hunting rifle. A fifty-millimetre lens gathers a little more light at the top end of the magnification range but sits higher on the rifle, which spoils the cheek weld and adds weight. Glass quality and coatings matter more than objective size for the low-light performance that decides the last ten minutes of a hunt; a good forty-millimetre scope beats a cheap fifty every evening.

Tube diameter

One-inch tubes are the traditional hunting standard, light and with the widest ring selection. Thirty-millimetre tubes give more internal adjustment range and slightly sturdier construction, and have become common on mid-price scopes. Either is fine; just buy the matching rings.

Reticles

A plain duplex reticle, thick at the edges and fine in the centre, is the best hunting reticle ever made: fast to find, easy to see against a deer at dusk, and uncluttered. Ballistic reticles with holdover marks are useful for open-country hunters who shoot past two hundred and fifty yards and have taken the time to confirm the marks with their load; for most deer hunting they add clutter. Illuminated reticles help in the last light against a dark animal, provided the illumination is dim enough not to bloom.

Focal plane

In a second focal plane scope the reticle stays the same size as you zoom; in a first focal plane scope it grows with magnification so the holdover marks stay true at every power. For a duplex hunting reticle, second focal plane is simpler and the reticle stays bold at low power, which is what you want in timber. First focal plane matters only if you use the reticle's marks for holdover at varying powers.

Bases and rings

Most modern rifles come drilled for bases or with a Picatinny rail already fitted. A one-piece rail with steel or quality aluminium rings is the sturdiest arrangement. Ring height should put the scope as low as the objective bell allows while clearing the barrel and the bolt handle; low is better for cheek weld and consistent aim. Buy rings and bases from a maker that publishes torque figures, and buy a torque driver to use them.

Mounting

Degrease the base screws and the receiver holes, apply a drop of blue thread locker and torque the bases to specification. Set the rings, place the scope, and adjust eye relief with the rifle shouldered in your normal position and the scope at its highest power, where eye relief is shortest. Level the reticle against a plumb line or a levelling kit, then torque the ring screws in a cross pattern in small steps to the maker's figure, usually fifteen to eighteen inch-pounds. Over-torqued rings crush scope tubes.

Zeroing

Bore-sight first so the first shot is on paper, then zero from a stable rest at a hundred yards with the ammunition you will hunt with. Fire three-shot groups, let the barrel cool between them, and adjust to the group's centre, not to the last shot. Most deer hunters zero an inch and a half to two inches high at a hundred yards, which puts a .308 or .270 dead on around two hundred and only a few inches low at three hundred. Confirm the zero after any hard knock and at the start of every season.

Scope covers, cant and the cold

Flip-up lens covers keep rain and frost off the glass on a wet morning and cost almost nothing. A small bubble level on the rail shows a cant that will push a long shot sideways. Nitrogen-purged scopes do not fog internally, but the outside of the ocular lens will fog when a warm face meets cold glass; keep a lens cloth in a pocket and let the rifle cool outdoors before the hunt rather than carrying it from a heated truck straight to the stand.

Budget

A sound rule is to spend at least a third of the rifle's price on the scope and mounts, and the same again if the rifle is inexpensive. A four-hundred-dollar rifle under a three-hundred-dollar scope is a better hunting rifle than a thousand-dollar rifle under a hundred-dollar scope.

Browse scopes, rings and bases and bolt-action rifles in the catalogue, and read the deer rifle guide for the cartridge under the glass. Your nearest public range for zeroing is on the city pages.

General information, not legal advice. Current as of September 2026. Laws change; check the official source before you act.