No. 4 Rifle; Zeroing Instructions Data Inconsistency?

[Surpmil]

As you say Johnson was a highly experienced shot, and the whole book is testimony to his devotion to accuracy and, by implication that of his superiors. He makes repeated references to the absolute necessity of accuracy in order for fire - and the solder - to be effective. The group sizes shown in the book as examples of what was attainable or desirable are much smaller than the acceptance levels of accuracy for the rifles and ammunition.

In the last few days I happened to be going through my stock of used front sight blades and examining them under magnification and yes, there are numerous examples of minor modifications to the blades. It would only make sense when a minor elevation correction was needed, but the lateral deflection was perfect. A new blade inserted would require the zeroing be repeated in both axes and that would be time-consuming process. The book makes reference to the soldier and his rifle being sent to the armourer at the range for adjustment as part of the zeroing process of the individual rifles to each soldier. With 30 or 100 rifles to correct one can see how an armourer might file a little off a blade rather than replacing the entire blade and effectively recommencing the zeroing process. Whether that was permissible practice I have no idea.

The proof of ammunition is interesting and I photographed the entire Canadian manual for that a few years back when I had access to it, but that process was about testing the accuracy of the ammunition, not the rifles.

Perhaps your point in citing that was to establish the accuracy standards of the ammunition and by implication that of the rifles? Alan d’Enfield has posted the acceptable accuracy standards for the rifles from the UK manual, and probably the same standards were adopted in Canada. And of course “Shoot to Live” was not written specifically for Canadian-made rifles or ammunition.

Regardless, unless ammunition of a higher than usual quality was used to test the rifles at manufacture, the accuracy standards for the rifles incorporate the expected and accepted variations in the accuracy of the issued ammunition. Can we now say where one began and the other ended?

The 6.5" MPI over POA mentioned in the UK manual gives no range of variation such as the 2 inches mentioned in Shoot to Live, but of course a range of variation existed in fact. Presumably it wasn’t thought necessary to mention as the NCO’s involved were expected to understand that some variation was inevitable and the measurement therefore an approximation? The lack of attention to this in the text implies it was not considered of great importance. A formation on the ranges to give the rifles their initial zero would soon find out what the particular lot(s) of ammunition on hand tended to do, and adjust accordingly.

My first thought was the same as yours that having the MPI slightly over the POA would be less desirable in combat than the reverse. That would depend on what if anything had been learned about the aiming habits of soldiers: did they tend to aim low or high in combat? Whatever the case, I mentioned it merely as an idea to be considered.

ARMOURERS' WING Precis No. SA/19A which implies the variation of MPI at 100 yards should be no more than 1.87".

What is the actual text and context? If this refers to the process of preliminary zeroing at 100 yards does it refer to the same variation which Shoot to Live gives as having an acceptable variance of 2 inches? Not a very large difference is it? 1.87" being effectively half of 3.75" one wonders about the context.

Regardless, Johnson describes this process as leading to a “rough zeroing”. Both manuals quoted refer to a MPI & POA coincidence at 300 yards. Shoot to Live states zeroes at 30 or 100 yards were preliminary and that the final zeroing would normally occur during advanced training and that this would be the zero that stayed with the soldier and his rifle throughout his service.

Logically the zero obtained at 30 or 100 yards would be mostly concerned with lateral error (windage). So considering that both manuals envisage a later final zeroing at 300 yards, the difference could amount to no more than where on the 300 yard target the respective authors preferred to see the first groups fired at 300 fall: higher or lower.

Perhaps you have already ruled out the types of targets used and the points of aim to be taken on them as variables that might explain this?

As we can see from this thread for example: h t t p s ://www.greatwarforum.org/topic/304772-external-ballistics-303-bullet/ there is plenty of debate about the rise and fall of Mk.VII ball and even about whether the formulas of the Textbook of Small Arms 1929 are entirely correct, so this variation between the two manuals is not so surprising in my opinion, nor significant given that the figures of 6.5" and 8.5" are merely points on a range of variation whose acceptable parameters overlap at 7.5 inches; whether that or indeed this whole matter has any significance in fact.

(The TBSA 1929 is of course based on the No.1 Mk.III and the harmonics of its lighter barrel and action rather than the No.4 Rifle; the No.1 Mk.VI gets only passing mention.)