No. 4 Rifle; Zeroing Instructions Data Inconsistency?

[Bindi2]

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.

[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 By the time I enlisted, the No.4 had been replaced by the C1 FN FAL, so I had no military experience with the rifle.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.

[Bindi2]

The bit you are missing is the difference in barrel harmonics between the two charges.

[Rick]

The bit you are missing is the difference in barrel harmonics between the two charges.

Thanks for the suggestion. But if that's so, the authors at Higher Niner of the various nations' pams, the 1950 Armourers' Precis, Reynolds, et al similarly also didn't notice the difference in barrel harmonics between the two charges in any version of the rifle.

None noticed sufficiently to even making mention of a significant difference in barrel harmonics between Cordite and NC loads, resulting in conflicting different zeroing data being required as in the Canadian Shoot To Live, based on whichever type of propellant was loaded.

As NC apparently was first introduced at the end of WW 1, and Cordite loaded ammunition was still in the supply system through WWII and then Korea, there is no certainty that a Commonwealth nation whose troops were in battle could be exclusively supplied with either Cordite or NC based ball ammunition to match whatever the troops' rifles were zeroed with prior to being sent into battle.

And a 2.5+/- MOA difference in zeroing is well over the difference of a single change in front sight blade height. So I would presume that Higher Niner, the ones developing and updating the pams throughout the service life of the rifle would have taken such a significant difference into account - even if only a simple notation somewhere within at least one of those publications, whatever version of the Lee Enfield it was attached to.

To fuel my academic curiosity about the two very different zeroing specifications, I have a range document from inside the Canadian Rangers with this related to zeroing their No.4 rifles:

LE Sites are calibrated to 174gr Spitzer Point Flat Base Mk7 Ammunition. Rangers are issued 175gr Spitzer Point Boat Tail Mk8Z Ammunition... Desired Point of Impact: 8.5" above the point of aim.

If Mk8z ammunition manufactured by IVI (or whoever in Canada) in the 1980's for the Rangers is in fact correct, at the suggested velocities for Mk8z ball ammunition, you would expect an even flatter ballistic parabola, and an even LOWER height above point of aim at 100 yards to obtain POA=POI at 300 yards.

[there's some confounding factors in these instructions in that the paper instructs zeroing at 100 meters, not yards, for a zero at 300 meters, not yards. And of course, with their issue sights calibrated for yards, I haven't bothered yet to see if a ballistic calculator says that a +8.5" POI works when sighting using metric instead of yards. I think a calculation of those ballistics, even with 300 meters being longer than 300 yards, you will still be lower than +8.5" at 100 meters to be zeroed with the 300 yard aperture at 300 meters.]

A shooting/rifle obsessed friend just retired as the RSM of his unit, and promptly joined the Canadian Ranger patrol nearest him. The Lee Enfield has been gone for a couple of years now, but I'm going to ask Gary if he can prowl what they have in the way of pams to see if they have anything there that relates to thus point of curiosity.

I also know Russ Meades as an acquaintance from way back in the day when he arrived here from the UK and enlisted in the Canadian military. Russ was pretty keen on shooting back in the day, and he ended his career decades later as the officer in charge of the Canadian Rangers; perhaps he can shed any light on it.

And finally, my brother retired from 30 years working at BATUS as a civilian whose working days were spent working beside British REMEs on the Challenger tanks and everything else mechanical that moved. He told me yesterday that one of the REMEs who stayed here is a Lee Enfield obsessed rifle nut, a good friend of his who I helped secure the recovery of a Land Rover (but why????), found multiple NATO documents on their military version of the DWAN that he printed out, which might relate to zeroing specifications. So perhaps there is something there as well...

Again, at this point it's purely an academic curiosity now that all the worthwhile Mk VII seems to have disappeared forever. But I do find a 2.5 MOA difference at 100 yards while zeroing these rifles to be interesting, with the Canadian disagreement with the other Commonwealth pams relating to zeroing this rifle.

Thanks again for the suggestions!

[Alan de Enfield]

As NC apparently was first introduced at the end of WW 1, and Cordite loaded ammunition was still in the supply system through WWII and then Korea, there is no certainty that a Commonwealth nation whose troops were in battle could be exclusively supplied with either Cordite or NC based ball ammunition to match whatever the troops' rifles were zeroed with prior to being sent into battle.

Cordite was used throughout the 'life' of the Lee Enfield and there are a number of period documents exlaining why the rifles should not fire ammunition of both types (Cordite & Nitro cellulose)

One example :

'Regulations For Army Ordnance Services', Vol.3, Pam.11A (1949) comments:-

APPENDIX 15

USE OF .303-IN CORDITE AND N.C. AMMUNITION

1. The action of Cordite propellant in the barrel of a .303-in. weapon is quite different from that of N.C. propellant.
Cordite gives a rapid build-up of pressure with great heat, leading to pitting and erosion of the chamber end of the barrel.
N.C., however, gives a more gradual build-up of pressure with less heat, and this in turn gives uniformity of barrel wear from chamber to muzzle, the amount of pitting and erosion being greatly reduced.

2. With Cordite propellant, set-up of the bullet is most pronounced and even when the chamber end of the barrel is well worn, the muzzle end still has sufficient rifling left to impart the necessary spin. As the wear advances up the barrel, so the accuracy of the weapon is progressively reduced.
With an N.C. propellant, set-up of the bullet is slow and by no means so pronounced, due to the more gradual building up of pressure. The barrel retains its original accuracy until wear reaches a critical stage, when a sudden falling off in accuracy occurs.

3. It can be seen by comparison with the effects of barrel wear that to use N.C. ammunition in a barrel which has fired Cordite will give serious inaccuracy in flight, whereas the use of Cordite ammunition in a barrel which has fired N.C. gives good accuracy, but serious changed the wear pattern of the barrel.
In the first case, i.e. a weapon which has fired Cordite ammunition the barrel will be eroded and fissured in the first few inches up from the chamber, the part in which obturation should occur. The poor set-up of the bullet, in the N.C. cartridge is not sufficient to give good gas sealing in such a barrel and the bullet does not, therefore, receive the maximum impulse. The resultant loss in velocity and instability due to lack of spin lead to a high degree of inaccuracy.
In the second case, Cordite ammunition fired from a barrel which shows uniformity of wear from firing N.C. ammunition, has an adequate reserve of set-up that ensures full gas sealing, with satisfactory velocity and spin. Unless the barrel wear is in a advanced stage due to firing a large number of N.C. rounds, there will be no immediate appreciable loss in accuracy. Furthermore, the decline in accuracy for Cordite ammunition will follow the normal gradual fall-off experience in weapons firing Cordite alone, as the wear at C of R progresses.

4. Trials have proved that even if only a few rounds of Cordite ammunition are fired from an "N.C." barrel, the ensuing accuracy life when N.C. is subsequently fired is reduced considerably. The occasional and restricted use of N.C. in a "Cordite" barrel will however, have little effect on its ensuing accuracy life for Cordite, although naturally the fire of N.C. will not be very accurate.

5. The effect of wear of barrels can be determined by firing shots through a paper screen at 100 yards. If, on examination of the screen, all shot holes are not perfectly round, then the barrel is no longer fit for use.
The danger lies in the fact that bullets fired erratically from badly worn barrels may overcome their instability in flight and take up a steady flight in the direction in which they happen to be pointing, with short-ranging and disastrous results if used for overhead fire. Except under these conditions of long-range firing there is no risk involved, though in normal range firing inaccurate fire will result.

6. The following instructions regarding the use of .303-in ammunition have been issued to users and are governed by stocks and types of ammunition and weapons in current use:-

(a) .303 in. Vickers M.G.s in M.G. Bns.

(i)Mk.8z only will be used for overhead firing.
(ii) Mixed belts, i.e. Ball, Tracer, A.P., etc., will NOT be used.
(iii) Any barrel which has fired Cordite ammunition will NOT be used for N.C.; barrels will be stamped “7” on the trunnion block and returned to R.A.O.C. through normal channels.
(iv) Barrel life for N.C. will be assessed by unit armourers using the appropriate gauges.

(b) .303 in. Vickers M.G.s in A.F.V.s.

Here the overhead fire problem is not considered; the range is usually less than is the case with ground M.G.s. tracer ammunition is required as an aid to fire control, and prolonged fire programmes are not envisaged. Special mixed belts of Mk.8z and Tracer are provided in boxes clearly marked “For use in A.F.V.s only”. The reduced life of the barrels is accepted.

(c) Light M.G.s.

Cordite ammunition normally will be used. N.C. ammunition, however, gives a relatively small flash at night and if the Bren is being used for a special purpose, e.g., on a patrol, its use is permitted.

(d) Rifles.

N.C. ammunition will not be used in rifles except in such circumstances as quoted in para. “(c)”
above, if necessity should arise.

7. Belt packed S.A.A. for M.G.s is packed in boxes which are clearly marked with labels or stenciling indicating its proper use. It will never be de-belted and used for practice purposes in L.M.G.s or rifles.

8. It must be noted that the above restrictions apply only to ammunition fired from British weapons. All American ammunition is N.C. loaded and their weapons are designed to fire it satisfactorily.


It is interesting to note that Lee Enfields that were authorised to use Mk8 (NC) ammunition had the barrel marked with an "8 in a circle"



See example #31

[Bindi2]

When our yardage ranges were changed to Metres we had to change the elevation slides on the sights as there was no corelation or do up dope charts. The POA used also had an impact. Civvie range shooting had the advantage of adjustable slides on the sights. Military sights did not they only had fixed marks. The only adjustment to zero was the front sight when changing POA.
Being a F Open shooter now days barrel harmonics and tuners with all sorts of tweak's with powder loads, seating depths to make accurate shooting shows to some degree how good the designers of the Lee Enfield system were.

[Rick]

When our yardage ranges were changed to Metres we had to change the elevation slides on the sights as there was no corelation or do up dope charts. The POA used also had an impact.

The differences would be true for any weapon in service when the issuing country converted to meters. The C1/C2 rifles which replaced Canada's Long Branch No. 4s were manufactured at Long Branch with sights graduated in meters, long before Canada as a country made the switch to metric.

If Canada ever changed the elevation slides on the Long Branch No. 4 rifles issued to the Canadian Rangers, I never saw or noticed that the times I was sent off to do SAI and/or RSO assignments in support of them. I believe (assume?) those rifles had the exact same sights they left the Long Branch arsenal with (or after an FTR at 202 Work Shop at Longue Pointe Garrison or Diemaco after about 1989).

But again, the Rangers or civilians using the original sights can choose whatever range/aperture sighting to zero at i.e. zeroing the 300 yard aperture at 300 meters instead.

But it still doesn't explain the fact there is a 2.5 MOA difference in zeroing instructions between that 1945 Canadian pam and the British and Aussie pams for the same rifle using the same ammunition from both before and after that 1945 Canadian pam.

Furthermore, you cannot fit either the Mk VII or Mk VIII ballistic parabola to have either a 300 yard POA=POI or a 300 meter POA=POI, and have POI at 100 yards be 2.5" above POA

[Rick]

Cordite was used throughout the 'life' of the Lee Enfield and there are a number of period documents exlaining why the rifles should not fire ammunition of both types (Cordite & Nitro cellulose)

Thanks for sharing that information once again Alan. I don't think I have a .pdf copy of that pam you reference when sharing that. If you have a web link to it, I'd like to add it to my small collection of old pams that I collect and read purely out of interest.

It is unlikely that a round of cordite or Mk VIIIz will ever be knowingly fired from my Lee-Enfields, but the topics of those days past relating to anything having to do with the infantry biz always interest me.

I have two battle boxes full of paper pams dating from the 1950's forward that the regiment had no interest in when I retired as they were all in with the latest .pdf versions of the pams. There are .pdf versions for some of them, but for others the military hadn't gotten around to yet. There was a rich collection of stuff from the Boer War, WWI, WWII, Korea etc (not the Regimental silverware and war trophies)... but the regimental museum's curators had wisely laid claim to anything that surfaced within the walls of the regiment from those eras.

Still, that information has nothing to do with explaining why there is a 2.5 MOA difference when zeroing at 100 yards between the Canadian's 1945 pam and the British and Aussie pams dating from both before and after that Canadian pam was published.