No. 4 Rifle; Zeroing Instructions Data Inconsistency?

[Surpmil]

As per the attachments to the first post in this thread "Shoot to Live" gives the MPI as 8.5 inches +/- 1 inch above POA at 100 yards. The "+/-" would seem to be the important point.

What if any range of variation in MPI at 100 yards is indicated in the UK manuals?

If the MPI is given as 6.5 inches presumably the range of variation would be 5.5" to 7.5"?

The Canadian range of variation is given as 7.5" to 9.5" so one can see the two(?) estimations presumably in a sense meet at the 7.5" mark?

The 2 inches of vertical variation provided for in "Shoot to Live" probably reflected a variation observed in actual range firing based on variations in rifles and ammunition.

My copy of "Shoot to Live" makes reference to the attack on Cherbourg in "the late summer of 1944", so the manual was presumably written or revised in late 1944 or sometime in 1945. Canadian troops in Europe were issued ammunition and rifles from British ordnance stocks so rather than a consistent quality of rifles and ammunition from Canadian sources, they could be issued any rifles and ammunition from any factories, British, Canadian or American. I have a Savage Mk.I* here which has the "US PROPERTY" barred out and several C Broad Arrow stamps for example. So estimations of what rifles and ammunition would do had to provide for variations in quality and consistency.

Both manuals agree that the MPI and the POA should coincide at 300 yards?

On page 198 it is stated: "It must be remembered that the recruit who has had his rifle zeroed at his basic training centre has only a roughly corrected weapon". It is also stated that some training centres would have only 30 or 100 yard ranges available, so the implication is clear that the 30 and 100 yard zeroes were preliminary to later zeroing at longer ranges. Was a final zeroing at 300 yards arranged before embarkation for theatres of operations? It would seem likely given the emphasis on rifle skills and accuracy which comes across in the 240 pages of "Shoot to Live".

On page 194, it is stated in upper case: "ALL ZEROING MUST BE DONE WITH BAYONET FIXED AND WITH THE BATTLE SIGHT OF WHATEVER MODEL OF BACK SIGHT IS ... AFFIXED TO THE RIFLE."

[Alan de Enfield]

On page 198 it is stated: "It must be remembered that the recruit who has had his rifle zeroed at his basic training centre has only a roughly corrected weapon". It is also stated that some training centres would have only 30 or 100 yard ranges available, so the implication is clear that the 30 and 100 yard zeroes were preliminary to later zeroing at longer ranges. Was a final zeroing at 300 yards arranged before embarkation for theatres of operations? It would seem likely given the emphasis on rifle skills and accuracy which comes across in the 240 pages of "Shoot to Live".

On page 194, it is stated in upper case: "ALL ZEROING MUST BE DONE WITH BAYONET FIXED AND WITH THE BATTLE SIGHT OF WHATEVER MODEL OF BACK SIGHT IS ... AFFIXED TO THE RIFLE."

At least in all factories under British control / management every rifle was tested and zero'd (without a bayonet fitted) as follows :


SMLE TESTING
For the SMLE All rifles were tested for accuracy by the Small Arms Inspection Department at 100ft, and 10% were also tested at 600 yds. All rifles were fired from a special mechanical rest, known as an Enfield Rest, and a special Telescope layer was used for laying an aim. The Enfield Rest was designed to simulate the conditions under which a rifle would be held when fired from the shoulder, and was provided with hand wheel adjustments for laying an aim. Trial shots were first fired and, if necessary the foresight was adjusted laterally, or replaced by one of a different height, until the shots on the target were within the required limits. Five rounds were then fired, and four of the five shots had to be contained in a rectangle 1 inch broad by 1½ in high. Rifle which failed this test were rejected. At 600 yds 10 shots were fired, nine of which had to fall within a 2 foot circle.

No 4 RIFLE TESTING
For the No 4 Rifle, the accuracy test was the same at 100ft ten per cent of all rifles were then fired at 200 yds when six of seven shots had to fall in a rectangle 6in x 6in , the point of mean impact having to be within 3 inches of the point of aim in any direction. Ten per cent of rifles fired at 200 yds were again fired at 600 yds when 6 out of seven shots had to be in a rectangle 18 inches x 18 inches the permissible deviation of point of mean impact being 9 inches up or down, or left or right. Two per cent of rifles were fired from the shoulder, ten rounds being fed into the magazine by charger and fired rapid to test “feeding up” and ejection. After these tests the barrel was inspected to ensure that there was no expansion in the bore or chamber and that it shaded correctly from end to end. (Was not bent)

No 5 TESTING
The firing test to which the No 5 rifle was subjected was the same as that for the No 4 at 100ft. It was not tested at 200 yds but 10 per cent were tested at 600 yards when the acceptance was ten out of ten shots contained in a rectangle 36 inches x 36 inches. Two per cent of the No 5 rifles were also submitted to the same functioning test as the No4 rifle.


Throughout World War 2 much of the accuracy testing was done by women shooters who quickly became proficient at the job. To speed up the procedure, the telescope layer was dispensed with, and aim was taken in the normal way through the back sight. The .1 inch aperture in the back sight was too large for easily laying a correct aim at 100ft, and a small spring steel adaptor was used.

[Rick]

What if any range of variation in MPI at 100 yards is indicated in the UK manuals?

I'm away from home putting my Griffon pup on some training birds over this Easter weekend, so I don't have my entire .pdf library at hand. But looking just at what I saved to my tablet, there is ARMOURERS' WING Precis No. SA/19A which implies the variation of MPI at 100 yards should be no more than 1.87".

In other words, no more distance than a change of front sight blade would result in then being closer to actual POA=POI. Each change of front blade size moves the POI either up or down 1.87".

If you were 2" in error from what POI should be, a change of sight blade should result in the POI being only .13" too high or low (as though that would be measured or measurable).

If your POI were 1.75" too high or too low, a change in sight blade would still result in a better zero. Now you'd be off in the other direction i.e. low instead of high or low instead of high, BUT now you'd only by off your desired POI by .1" of an inch.

By changing front sight blades, you should be no worse than +/- .9" inches from the desired POA=POI at 100 yards.

In the civilian world, many a front sight blade has given it's life to be put on a rifle and then the owner carefully dressed down the blade until they got the desired POA=POI with their desired load, at whatever distance they wanted one of the calibrations on their rear sight to be true at.

I would be surprised if more than a few regimental rifle teams DIDN'T do the exact same thing to get POI=POA as true as possible, rather than just "closest you can get with the front blades available".

If the MPI is given as 6.5 inches presumably the range of variation would be 5.5" to 7.5"?

The Canadianicon range of variation is given as 7.5" to 9.5" so one can see the two(?) estimations presumably in a sense meet at the 7.5" mark?

No. What you're visualizing is the overlap of the Figure Of Merit specified for the ball round/rifle combination by the Canadians versus the other commonwealth nations. Whether Brit or Canadian, whether the specified Figure of Merit grouping requirements are identical in size or different, you will ideally zero so that POA=POI is centered in the middle of the group within that Figure Of Merit.

You would adjust as best you could with the front sight height variations available to center on the middle of the group, whether the rifle put them all in a 2" group or a 4" group.

The 2 inches of vertical variation provided for in "Shoot to Live" probably reflected a variation observed in actual range firing based on variations in rifles and ammunition.

No. Or, no, I don't think so.

Remember that there are Figure Of Merit grouping standards for both the rifles and the ammunition itself no matter what Lee Enfield it ultimately ended up being loaded into out on the FEBA. Those Figures Of Merit are the limitations on what is allowed in variations in both the ammunition and the rifles.

I can't prove my opinion is right, but no, I don't think so. First, the author Johnson was an accomplished international Bisley/Palma competitor who had captained the Canadian team multiple times. That, and the focus of the book on SAIs effectively teaching the troops marksmanship doesn't lead to thinking the book was accepting of a completely different zero because that would somehow or other address mediocrity/lower quality rifles and ammunition.