So would you say that optical sights have no advantage other than for snipers or low light gear?
Well, this is a very thorny issue, so if you'll indulge me for a minute - as well as shooting for the Parachute Regiment and the Army, I've been shooting for Wales for some time now, so I like to think I have too much experience just to put it down to 'yes' and 'no'.
Optical sights make the target appear bigger. You're right to identify the two situations in which this is very much advantageous - at very long range, where the target is too small to be easily seen, and at night, where radioactive compounds are used to allow the rifleman to see the target as if it were illuminated. They are useful in these situations because you simply can't aim at the enemy without one; if you like, they become the least-worst option (another advantage at long range is that the crosshairs are normally marked with minute-deviations from the centre, allowing you to adjust for minor changes in wind and light without coming out of the aim to adjust the sights themselves).
The reason I prefer iron sights boils down to the causes of innaccurate shooting. In an inexperienced or badly equipped shot, most error is down to the handling - the weapon is moving up and down from the breathing, or the shots will go off laterally because the weapon is twisted, or it's simply shaking around because the shooter doesn't have the support to hold it exactly on target (bearing in mind that a bullseye on a TR target is one-thirtieth of a degree across - you're aiming at an apple from 300m). However, most experienced shooters using a sling (or a bipod, or even the magazine as a monopod, as the Army team used to on the SA80) will have the vast majority of the error coming about from what I call 'point-of-aim deviation' - literally pointing it in the wrong place. This is generally the result of an error in perception of where the centre of the fore-sight actually is (to illustrate this, draw a circle and put a dot in the middle, then measure it to see how close you are).
Since the deviation is
absolute rather than a percentage of the sight (try doing that test with a very big circle and a very small circle, and see what
percentage error you have), a sight which magnifies the target by four times also magnifies errors of this sort by four times. With highly exact sights like those you find mounted on the top of sniper rifles, this isn't a problem - the increased precision of the sight itself more than compensates for this effect. However, with sights like the SUSAT which are intentionally not so precise (the Army wants its riflemen to maintain a high rate of reasonably accurate fire rather than take six weeks to take the perfect shot and as a result be unable to suppress the enemy), it becomes very obvious indeed. As such, equipping normal service rifles - in a military such as ours with high standards of marksmanship - with optical sights will lead to a decline in accuracy. Of course, the Army redesigned its marksmanship tests in light of this, and, surprisingly, SUSAT-equipped SA80s are being hailed as the most accurate rifle in the world under these tests.
