How much magnification do you actually need?
Updated 2026-09-20
Less than the number on the box suggests. A deer at 300 yards is a comfortable shot at 6× to 9×; hitting steel at 1,000 yards needs 15× to 20× to see the target well, not 35×. High magnification buys identification and spotting your own hits; it costs field of view, exit pupil, and a wobble that grows with the image. Buy the bottom of the range for the shooting you do most and treat the top end as a bonus.
A working rule
Up to about 10×, one power per hundred yards is a fair guide: 3× for a shot at 300 is tight, 9× is comfortable. Past that the rule breaks down, because past 300 yards the limit is reading wind and holding still, not seeing the target. Most precision shooters run 12× to 18× for shots at 800 to 1,000 yards and turn it up only to spot impacts. The 30× and 35× scopes exist for benchrest and for reading mirage, not for making the shot easier.
What high magnification costs
Three things. Exit pupil — the objective divided by the magnification — shrinks as you zoom: a 50 mm objective gives a 10 mm beam at 5× and a 2 mm one at 25×, and below about 2 mm the image dims and your eye has to be exactly in place. Field of view collapses, so finding a target and following a moving one gets harder. And every tremor in your hold is magnified with the picture, which is unnerving and makes people shoot worse than they would at lower power.
The bottom number matters more
The lowest magnification decides what the scope can do up close and how quickly you can get on target, and there is no fixing it later. A 5-25× cannot do a 100-yard running shot; a 3-15× can. On a carbine, a true 1× — where the image is the same size as with the naked eye — is what lets you shoot with both eyes open. Decide the bottom end first.
The zoom ratio trap
An 8× or 10× erector (1-8×, 3-30×) is a genuine engineering achievement and it costs money. At the same price, a 4× or 5× ratio scope usually has better glass, more forgiving eye relief and a bigger sweet spot behind the eyepiece. Pay for a wide ratio when you will really use both ends; otherwise buy the narrower scope that does one job well.
Where the classics land
The 3-9×40 became the default deer scope because every number in it is a good compromise. The 1-6× and 1-8× took over carbines for the same reason. The 5-25×56 is the precision default because 25× covers a thousand yards and 56 mm keeps the exit pupil usable there. These layouts have survived because the maths works, and the catalog's hub pages sort every scope by exactly those numbers.