No. 4 Rifle; Zeroing Instructions Data Inconsistency?

[Rick]

I have never been able to match Cordite and Nitro loads on the range chart with the rifle sight markings at the same FPS. We had to make our own dope sheets

Unless I've forgotten, I don't think we were ever issued Mk VII ammunition from the DCRA that was cordite; I imagine it was all used up by that point, 30 years after the WWII ended and 20 years after Korea. By the time I enlisted, the No.4 had been replaced by the C1 FN FAL, so I had no military experience with the rifle.

That aside, we know you have to adjust your come-ups at longer ranges due to the differences between lots of ammunition. But perhaps more specific to the question, a couple of things:

1. With all the detail provided in the Brit military pam, if there was a significant amount of ballistic difference for the average infantryman between the original cordite and then after the ammunition was loaded with smokeless, I would expect that at some point in the Armourer's pam there would have been a notation on zeroing differences when cordite was being used and when smokeless was used. What pams and material I have read is silent on any significant differences.

2. A 2.5 MOA difference at 100 yards between the two sets of zeroing data is an enormous amount that I doubt the difference between cordite and smokeless could potentially explain.

3. If you try getting a grip on how such differences could be possible, pick your ballistics software of choice, give the Mk VII round a G1 B.C. of about .467 and a MV of about 2440 fps. Then look at the manipulations to muzzle velocity, etc you have to make in order to produce a ballistic result where POA=POI at 300 yards - and a height above line of sight at 100 yards that is 8.5".

On the other hand, the zeroing data provided in the Armourer's precis is pretty much bang on when fed into a ballistics calculator. The Canadian data in the 1945 Shoot To Live just does not fit.

My assumption is that I am missing something, somewhere, but the Canadian zeroing data just doesn't fit.