Enfield Optics > Explanation & Lesson > Spectacles, Diffraction and Aiming Off
Explanation
My previous conversations with myself had been like, ‘What am I doing here, shooting at this pale-grey, shaggy-carpeted rugger-ball and why is its major axis revolving like this?’ So much gritty concentration was being expended on trying to fine-up the horrible sight-picture that there was precious little to spare for ensuring consistent holding and sear release. My worsening eyesight was in fact the root cause of my problem and not in any physical, optical sense; the problem was psychological. Removing the resulting mental or ‘concentration’ block was all that was needed.
During the .22 experiment I had not worried about the sight-picture definition because I had said ‘Accept the sight-picture in order to quantify it’. I was therefore able to relax happily and ‘do the best with what I’d got’ and there was plenty of concentration left over for seeing to the gun-holding and triggering; the eye itself was also less strained because the shots were got off with only a few seconds on aim.
Lesson
After years of perfect eyesight the psychological acceptance of a worsening open-sight picture is difficult but the seriousness of the defect is widely over-estimated. Expenditure of extra eye concentration effort to try to counteract this mild defect is actually counter-productive. Given the use of an eye lens of optimum focal length (if needed) and open sights which permit the use of a reasonably 6 o’clock aim, the contribution to group size diameter (error) arising from aiming errors will be small compared with the contributions arising from poor sear release etc. Quite a large aiming error is needed to shift a potential 10 to an 8, but a perfect aim and a snatched trigger will easily shift it to a 6! This truth is obscured in Enfield shooting for statistical reasons. If the rifle is capable of grouping within the 8 ring, any perfectly aimed shot has a good probability of being only an 8, and by the same token a badly aimed shot can turn up as a 10! It is not obscured in .22 rifle shooting because of the extra precision available. My own experience is that if one deliberately aims off the least amount that is observable, as a definite non-central aim, and then a little bit more, the result is likely to be no worse than a 9. Try it for yourself with a .22 rifle fired from a sand-bag rest.
At the moment, in Enfield shooting, a competent shot is having to count some 8’s along with his 9’s and 10’s. To score 90 he has to fluke as many 10’s as he gets 8’s. Closing the group, in order to get those 8’s half over the 9 ring will also sometimes push the occasional 9 into the bull. To do this he has to improve everything (eg bullet/powder/bore marriage, holding, breathing technique, triggering, aiming precision) and trying to get to the ultimate in aiming precision will probably make the least contribution, until he has got the other things as right as possible. Getting the priorities right and apportioning one’s concentration correctly between the various needs will make for the higher score. At least, that is how I see it
Now, having looked at a problem presented by an ageing eye lined up with open sights and an aiming mark – a problem which I propose is not as serious as one might think – let us go into a little more detail.
With age the extent to which the eye-lens can be flexed in order to produce a variation in its focal length (strength) progressively reduces. Thus, when I was 10 I could focus sharply on all objects between infinity and 5 inches from the eye. Nowadays I can focus on all objects between infinity and 10 feet from the eye. I need reading glasses of course, whereby the eye lens system is artificially strengthened and a sharp image of print can be brought to focus on the retina. However, with reading glasses on I can no longer focus objects at infinity because I cannot then sufficiently unstrengthen my eye lens by muscular effort (100 yards and on, is ‘infinity’ for practical optical purposes). The aiming mark at 100 yards is a very vague blur seen through reading glasses. If I use a lens weaker than is required for reading but which just enables me to bring the Enfield foresight comfortably into sharp focus when I am in the firing position, the aiming mark at 100 yards is slightly fuzzy. It is going to get worse as the eye lens gets more and more inflexible as it ages further, but the distress is psychological more than a seriously debilitating optical fault so I am getting myself used to it.
Thus, I now have a choice. Without glasses I see a fuzzy foresight and a sharp aiming mark, and with optimum glasses I have a sharp foresight and a fuzzy aiming mark. Which is the best choice? The answer is definitely the latter. Consider, in the first choice a misplacement of the indistinct foresight in the overall aiming picture is possibly due to it being indistinctly set in an indistinct rear sight. Say the misplacement error due to fuzz is 50 thousandths of an inch. If the foresight is one yard from the eye the shot-position error at 100 yards is going to be 5 inches; quite a disastrously bad shot. In the second choice, the error is due to fuzziness of the aiming mark and the clear foresight can be misplaced ie placed differently in or near the fuzzy area, from shot to shot. However, the judgment from shot to shot, as to where the effective boundary of the aiming mark really is, is not likely to have an error of more than one inch on the target face. The 10 you might have got with one judgment will be no worse than a 9 with another judgment of the fuzz. So, get a lens of the right strength, see the foresight clearly and go on hitting the pale-grey, shaggy-carpeted football right near the middle, right up to cease-fire or Gabriel’s toot.
