For your Information - Someone posted this, but I no longer know the web address. Bill
Ross Mk.3 backsight
This description of the Ross sight appeared in the British Rifleman for Sept. 1942. Can anyone fault it?
OUR military authorities occasionally issue weapons, especially to the unfortunate Home Guard, with totally inadequate, and some cases complete absence of, information as to how to use them. The Ross rifle is a case in point. Most people manage eventually to worry out the mysteries of the bolt, but generally the backsight defeats them. The Editor has asked me to ensure that readers at least of The Rifleman shall be properly informed.
There have been several variations of this sight issued in past years, but all those I have seen in this country are of the model described here.
It has two “Battle Sights,” which are cut-away apertures both fixed to the slide which also has an ordinary or closed Aperture.
The normal position of this slide is, of course, at the bottom of the Leaf, and the Leaf down.
The Battle Sight which then shows is set for 600 yards. NOT 400 yards. There is no 400 yard Battle Sight on this Ross.
If you now flip up the Leaf, the other Battle Sight shows.
This is (with the slide at the bottom as stated) set for 1,000 yards.
The idea is that, against an advancing enemy, the soldier starts shooting, with this Battle Sight up, when they are 1,000 yards away, and until they reach 600 yards away. He then flips the Leaf down and continues with the 600 yard Battle Sight aiming down (if he knows the trajectory) when they get closer. A very good idea, too—if anyone were ever told about it.
Both these Battle Sights have, as I said, cut-away Apertures. They are variously referred to by the ignorant as “ Open sights,” “Modified U’s,” “Buckhorns,” and all kinds of things ; and instructors instruct recruits to “ get the blade in the centre of the U and level with the shoulders.” It is pathetic! Imagine any rifle designer fitting an open sight at two inches from the eye! Not outside Bedlam.
No—use them exactly like any other aperture. Just imagine, if you like, that the bit of the ring cut away at the top is still there, and go ahead. It is cut out to let more light through in bad light, and to enable you to pick up your object quicker. But as no British soldiers or Home Guards ever practise shooting in dusk at natural targets, they would not know this. Nor would they know anything about the virtues of white sight-paint and shooting with both eyes open—things which the stalker learns in his cradle and which soldiers should be taught but never are. However, we are supposed to be talking about the Ross Sight.
As stated, there is an ordinary Aperture, at the bottom of the slide, which has the 1,000 yard Battle Sight at the top.
This Aperture is for all accurate deliberate fire. It is raised up the Leaf by a quick thread screw, and on the face of the Leaf are Range Markings in yards. This series of figures starts at zero, and then 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 hundred yards. There is no 100 yards. One hundred is never used as a range marking in war, and if you want to set your sight accurately for 100 for practice (grouping) you have to find the elevation, somewhere above zero, for yourself.
On the right edge of the Leaf is a Scale. This is not another series of hundreds of yards markings. Its zero is level with the other zero. There is no other connection. It is meant to be used, for targeting the rifle, exactly like the scales on civilian .22 rifle sights, which have no ranges marked on.
This scale is marked from One to Nine. These are tenths of an inch. Each division is again divided up into four.
One-tenth of an inch, at this sight radius, gives you, near enough, ten minutes of angle. A quarter division therefore gives you a quarter of this, or 21 minutes of angle; and this is the finest adjustment shown. There are no “clicks” but you can of course set the sight to finer adjustment by judgement. The scale is probably intended chiefly to enable a man to take exact readings of the sight on this scale for the various ranges, if the rifle does not agree exactly with the range markings, as it seldom does, owing to the impossibility of standardising precisely such things as stocking and barrel flip and jump.
Behind and at the bottom of the Leaf is a triple knurled head which works the Windgauge. There is on the front of the Leaf a Windgauge Scale marked in twentieths of an inch. Each of these, of course, gives five minutes of lateral angle. They are not divided any more finely, and intermediate settings are obtained by the knurled head.
The windgauge is, of course, a very convenient means of adjustment for straight shooting. It should then be left alone. Wind allowance is not done now by windgauge in military shooting.
By the way, there is a very simple way of checking the range to which these, or any other Battle Sights are supposed to be set, as follows.
Fix the rifle firmly in a vice or the like, with the 600 yard Battle Sight and foresight lined up correctly at a mark - any mark, at any distance. It doesn’t matter.
Now raise the Leaf (without moving the rifle) and screw up the slide until the Aperture in the bottom of it comes correctly to the same aim. If you have done it right, you will find that it has come up to the 600 yards mark. That is your check.
Similarly, with the Leaf up and slide at the bottom, line up the Leaf Battle Sight with the mark. Then screw up the slide until the Aperture comes to the aim. It will be at the 1,000 yards mark.
You can check a P.14 or M.17 similarly, when with the P.14 you will find that the Battle Sight aim agrees with that of the Slide Aperture at 400 yards, as a rule. I have found a few which were set for 300 yards. The Battle Sight on the M.17 agrees with the leaf at 450 yards. This is because the Battle Sight is identical and the same height on both rifles, and thus gives a longer range, by 50 yards, to the higher velocity .300 cartridge. The leaf sights are not the same, each being correctly marked at the range elevations for its cartridge.
I agree. Can you imagine trying to explain that instruction to a bunch of raw recruits fresh off the farm only interested in the big adventure, women and wiskey.... not to mention riflemen like us here... FORGET IT. 
