Iron sights are not dead yet, but this 18th-century technology needs to expire. It has hung on as long as it has due to the innate conservatism (technical, not political) of the gun culture, and due to the persistence of myths about optical sights — and low-cost, ultra-low-quality optical sights that reinforce the myths.
What’s good about iron sights
Well, to start with, they’re iron. That means there’s no glass to break. A tumble or explosion that breaks a sight would be enough, for instance, to bend a barrel, and there’s no securing against that. They’ve been around for a long time, and so everyone knows how to use them, or thinks he does, at least. They’re small and low-profile, in most cases, important when dealing with handguns particularly. And they often come “free” with the gun — don’t underestimate the effects of that “bundling” on iron sights’ market penetration.
What’s not so good about iron sights
They’re aligned slightly differently for every user, to one degree or another. While you often can pick up and shoot somebody else’s sighted-in scoped rifle to point of aim, you’ll have more difficulty doing that with an iron-sighted rifle.
The sights are difficult to align, and require explicit training in the somewhat unnatural learned behavior of sight alignment. Furthermore, an error caused by improper sight alignment is much more serious than an error caused by, for example, improper sight picture or improper breath control.
Most importantly of all, ocular biology means that our inborn sighting tackle has a relatively narrow depth of field. Meaning that, if you focus on something a certain distance in front of you, your focus on things that are nearer and farther is degraded. That is the reason that you are instructed to focus on the front sight blade in basic marksmanship instruction — you can’t focus on that, and the rear sight, and the target; you have to pick one. That is the reason that, among iron sights, ceteris paribus, a peep sight is a much more accurate sight than a notch rear sight (it is more readily aligned when out of focus).
Iron sights vanish in conditions of low light. So do normal telescope reticles, but illuminated scopes make up a higher percentage of that kind of combat sights than illuminated iron sights. (We’re big fans of tritium illumination — with all its failings — for both kinds of sights). It’s a sad fact that most civilian (including police) engagements happen in low light conditions, as do a large number of military engagements. While being able to see in the dark (like soldiers do with their NV goggles or monoculars) is the gold standard, at least being able to see your sights in the dark is a great advantage over individuals equipped with standard factory sights.
The advantages of an optical sight
An optical sight can provide: passive light gathering, a single focal plane, and magnification. Each provides a different kind of advantage; together, they add up to huge superiority for optical sights.
“Light gathering” is the term used in the rifle optic world, but the unfortunate fact is that it is a lie; optical sights have no gain (or actually, negative gain). There is no way an optical (non-electronic) scope can put out its ocular lens (the end near your eye) any more than it takes in at the objective lens end (the end near your target). So what “light gathering” really is, is a high percentage of light transmission (which must be less than 1, so a superior scope is in the 0.98 light transmision area, an fair one 0.93, and airsoft crap and Walmart specials about 0.8 and 0.9 respectively. What you want is the largest possible “exit pupil” and objective lens you can get. (Rule of thumb for exit pupil in mm: Objective lens size in mm,
times divided by the magnification. Therefore, as the day’s light dims, you can see more through a variable-power scope by dialing the magnification down).
These Japanese warship glasses have a 120mm objective lens.
The benefit of a really big exit pupil (and therfore a really big objective lens) is frequently underestimated, but hunters have known about it for years. It’s especially advantageous in morning or evening twilight, when game tends to be highly active. They’re not the only ones, of course. In World War II, Japanese warships had a significant advantage over Allied ships in night engagements, because the IJN had equipped its vessels with binoculars, optical rangefinders, and weapons sights that had superior optics in general and superior “light gathering” in particular. One way the Japanese did this was by making stuff with monster sized objective lenses. (They were also wprld-class at lens grinding. Nikon didn’t spring fully-formed from Zeus’s brow after the war, you know). With a large objective lens and a large exit pupil, you can feed more light into your own pupil, which is probably somewhere between four and eight millimeters in low light, depending on your own age and anatomy.
Of course, the larger an objective lens is the more difficult its manufacture is, and — you knew there was a tradeoff, didn’t you? — the more it costs.
You might have thought we covered focal plane enough above, in our discussion of sight picture. But the focal plane advantage isn’t just about sight picture. Seeing your point of aim superimposed directly upon the target lets you see how your breathing and position influence the motion of your aim point on the target, and therefore increases your probability of hitting and killing the target.
Finally, optical sights can provide magnification of the target, which has aiming benefits and also tactical benefits (it’s a reconnaissance tool, amplifying human senses). You may not carry a binocular, given all the other crap you have to haul,
Why the military resisted optical sights for so long
Military shooters first used telescopic sights in the mid-19th Century. Civil War snipers had scopes, based on target-shooters’ scopes of the day. But the Army here, and other Armies worldwide, resisted them for general issue. There were two objections to optical sights, one technical and one cultural.
In war, the cultural is to the technical as three is to one, to disrupt an epigram of Napoleon’s. So the cultural objection — that using an optical sight is somehow cheating — has been the dominant one. (Some units still resist using issued optical sights for marksmanship refresher training, and then expect troops to use them effectively in combat).
The technical objection — the fragility of scopes — was overcome by events sometime in the 1960s. The M16A2 style rear sight is more readily disrupted than a well-built modern service scope, like an ACOG. But before we had anvil-tough ACOGs, our guys had to work their way through the zero-losing Warner & Swasey of WWI, the fog-prone-if-not-coddled Lyman Alaskan and Weaver scopes of mid-century, and the brilliant but fiddly Leatherwood ART II that made the M-21 deadly — when it worked. Each was an improvement over its predecessors, as were the Unertl and Leopold Ultra M3A used on more recent sniper weapons (The Ultra M3A was better than the Mark IV that replaced it in Leupold’s line; it was only replaced because it cost a fortune to manufacture). But it took the example of our British cousins to move us to optics for everybody, not just sharpshooters.
The British Army, which is often accused of having centuries of tradition untrammelled by progress, and might still be selling commissions if that hadn’t gotten their asses handed to them in the Crimean War, went to an optical sight early — a fixed 1.5x power, Tritium-equipped unit called the Sight Unit Infantry Trilux — and never looked back. Three decades of British success with the Trilux let the US military, special-operations-forces first, dip its toes into the optical water. Once the Joes started using scopes — ACOGs — the inherent advantages of modern optics made sure that the scopes were here to stay.
It didn’t happen all at once. After the success of the ACOG on the carbines of
Spacial Special Operations Forces, first the Marines, who are always a bit more forward-thinking than the Army, and finally the Army went to ACOG optics as well (these slightly different versions all are good choices). In addition, the Army issues the Canadian-made Elcan M145 optic for light machine guns. SOF has a later Elcan, the one sold on the civilian market as the SpectreDR, and it has received mixed reviews — it is beautiful glass with an interesting 1x and 4x dual-magnification capability, but it doesn’t match the ACOGs for durability. And if you’re buying it yourself, its extremely expensive.
In addition to these sights, the military uses Aimpoint red-dots and EoTech holographic sights. We’ve shot ‘em all and for everything but close-range use, we come back to ACOGs.
Picking the right optical sight
The aphorism that applies here is horses for courses. The right sight for an under-bed home-defense AR is not the right sight for popping jackrabbits (or people) at 300 yards. So you begin with a major division between red-dot and holographic sights for close range, and scopes for medium and long ranges. For general purpose use (i.e., not for a dedicated CQB gun) we strongly recommend a scope over a red -dot, and for CQB we almost always recommend a red-dot over a holo — which is another post, but one reason is battery life, which is ridiculous: ridiculously short for EoTech, ridiculously long for Aimpoint. (The EoTech has some specific advantages but as we said, that’s another post).
Field of view needs to fit the mission. If most of your shots will be under 200m, and your targets are motile, a Leupold Mark IV is not only overkill, it also is much too narrow a picture. You’ll constantly be transitioning from head up, scanning, to head down, sighting. This is, to steal a line from the President, “not optimal.” And in general, field of view and power are inversely related. If you’re popping steel targets at 1600m with a .50 BMG rifle from a bench rest, 28 power is probably useful to you. If you are hunting deer, elk, or the Independent Wealth Redistribution Technician™ in your family room, it probably isn’t.
The world’s militaries seem to think a 1 to 4 power scope is best for hunting homo sapiens. What good is one power? All the good in the world. It puts the target and the aiming point in the same focal plane and gets you on target fast.
While SF went to the very expensive Elcan, we’re huge fans of the much more rugged Trijicon ACOG. The ACOG TA01NSN is the one from the SOPMOD I kit and is an excellent product. It is as nearly indestructible as any scope ever made. (That said, we’ve recently heard a litany of broken-ACOG stories, and the guys still serving say the newer ones are even more durable. And we’ve seen a lot of insults delivered to an ACOG that kept zero and kept on rocking).
Do you need night vision compatibility?
This adds to the capability, but it also adds cost and complexity, and very few of you will ever use it. Do not spend hundreds of dollars for this “in case.” If you do not currently use night vision devices, have access to them and practice with them, are you really going to use that capability? Humans are creatures of habit, and you will almost certainly keep doing what you’re doing now, even if you spend a lot of money on a new gadget. If NODS compatibility becomes important to you down the range, trade your non-compatible sight in.
Wrapping it up:
So that leaves us with an understanding that almost any scope beats no scope, and with an optical sight checkist that looks like this:
- _________________________ is my intended use
- a wide/narrow field of view works best for that (pick one)
- My minimum and maximum power requirements are (if you don’t know, 4-power is a good all-round scope)
- I do or don’t need: variable power (default, no)
- …Night vision compatibility (default, no)
- Name brand and warranty. (You will probably never need the warranty for your scope. If you do need it, though, you will need it very badly. A company that stands behind its products is also an indicator that the products weren’t just slapped together in the first place. And yes, you pay for that).
It’s good to buy the best scope you can afford, within reason, as long as you are planning to keep the weapon. If you think you might resell it later, bear in mind that used scopes depreciate more than used guns do, and when you sell, you’ll probably do better separating the weapon and scope and selling them separately.
And finally, before you buy it, try it. If the eye relief suitable for your application? (We can walk into any large gun shop and find used guns that have scopes set up with bad eye relief. Eye relief is also inversely related to magnification, in general terms).