WW1 'Periscope Prism company' sniper scope???

[Roger Payne]

Very cogent surpmil! I am inclined to agree that the Hensoldt could just have easily been a Voigtlander, a Goerz, or an Otto Bock, & also that the Aldis is just as good an optic as those. But as we know from many instances, the enemy's kit is much better than our own.........except that whilst the perception is sometimes correct, it is by no means always. In the SAC minutes there is considerable discussion over the lateral adjustment issue, & the decision seems to fall in favour of the fitting of the prisms (well, they did go ahead & do it!) over an optically simpler scope & lateral adjustment on a mount leg. Even so, the relative merits of twin screws, one tightened as the other is slackened off, is debated against the usual German method of a single transverse worm screw. The SAC minutes make the point that if a laterally adjustable mount were to be used then the twin screws is a better idea as there is less propensity for backlash developing as the threads wear with use. As they were clearly thinking in terms of fitting the modified Aldis scopes (prism fitted) to the P'14 rifles which were being trialled over this period, what on earth made them abandon it in favour of another plagiarised German scope that at best was only the equal of the Aldis, & in some ways its inferior?? Or perhaps the answer is as simple as mentioned near the top of the paragraph.......all down to perception.

[Surpmil]

Yes, I should qualify my previous comment to the extent that as you point out, the Patt.18 does eliminate the windage adjustment issue with claw mounts, by moving that adjustment to the rotating prism in the objective cell. (Edit: erroneous evaluation of contact between crosspin and front claws removed!)

But as far as being durable, accessible and simple to use, I'm not sure the prism idea is much good: not only hidden behind that very fragile brass cover, but only adjustable with a special flat key and every time you adjust the windage, you have to correct the range drum as well. Even for those with only two thumbs working with those key slots without mashing them up isn't easy is it?

At least with the typical Germanic square key you could grasp the key with a small wrench if you had to, or find a suitable key in clock-maker's shop; very common in those days of course.

The double opposing adjustment screws were indeed an improvement on the single screw as you say, as allowing screw backlash to be taken up as it developed. Once the single screw type develops backlash it's back to base workshop, and those dovetails and threads were so close fitting, ----- help you if you allowed moisture to get in and quietly rust it solid! And as you know from working on them, those prism cells are inclined to go solid as well...

The only advantage to the Patt.18 I can think of it is a bit less weight and therefore a bit less stress on mounts from recoil/"rebound" on firing.

Yes, one has to be careful of the tendency to see the opponent's equipment as always better - at least as cautious of the tendency to do the opposite!

[lmg15]

Some very good insights there that get me thinking.... I have had a bit of experience with the manufacture of the front mounting blocks for the Patt.18, and as a result have had to consider some of these things from both practical and theoretical points of view.

It is hard to know all the steps that PPCo considered in the evolution of the Patt.18 mount system, but I think that the theoretical failings of the German shallow claw system (as you very cogently spell out above) were understood by PPCo. The ability to use the Aldis lateral adjustment prism gave them the opportunity to make the scope and rifle mounts as rigid, simple and solid as possible, while still allowing for quick detachment.

That brings us to the question of whether the PPCo system was the best in practicality and execution, but without some objective evidence, it is hard to say whether the Patt.18 system of mounts was a practical improvement over the German shallow claw mounts. That would probably come down to things like no wandering zero and repeatability (ability to keep MPI after when the scope is mounted/dismounted from the rifle over and over), when compared with its German counterparts. Maybe PPCo had such faith in the rigidity of the Patt.18 system and its corresponding repeatability, that the PITA prism adjustment was something not required often enough to be a real PITA?

In terms of the practicality of execution from an engineering perspective, The level of commitment to precision in the PPCo mount system is very high, given that it is also designed for a high degree of interchangeability between rifles and scopes (notwithstanding the scopes still being serial numbered to the rifles). This means that any significant factory of field hand fitting is not on the agenda, as opposed to almost every German WWI sniper rig I have seen (maybe with the exception of the late war Goertz semi turret system).

So with that in mind, the use of the transverse pin in the front rifle mount must allow the scope only one degree of freedom when it is attached, being movement backwards and forwards. This has to be done with extreme precision in terms of eliminating any vertical movement whatsoever, so its diameter, in turn, has to be a very fine tolerance fit into the notch of the scope mount claw. The rear scope mount is locked rigidly into the rear rifle mount with a slight interference fit with the semi cylindrical locking catch / cam (it should tighten up a little and the thumb lever is rolled over to lock in the rear scope leg). Hence you have complete rigidity with the scope locked in both vertically and horizontally.

The lateral degree of freedom is addresses by having fine tolerances and large bearing surface areas between the front rifle mount slots and the claw blades. Similarly fine lateral tolerances on the rear mounts too.

So, that's the theory, but how practical was it? Well, having tried to make a set and measuring pins and slots to the point of near insanity, I can vouch that the fine tolerances required were executed well by PPCo (and not necessarily by me). Also, having done one pair of front rifle mount blocks, I am pretty certain of the exact manufacturing sequence required to achieve the required outcome, and for a well set up shop, it is eminently do-able, with one pair of identical blocks coming out of each set of operations.

So that is my insight from personal design and manufacturing experience.

As an aside, I cannot understand why the Accumounts versions of the rifle blocks are so poor when they could be much better for just a little more effort. That notes that you cannot fit an original Patt.18 scope onto the Accumounts front block because the pin diameter is too big, and has to be ground out in the middle to fit it onto a receiver ring. The Accumounts rear rifle block has paid vague homage to the original, but in all other respects has gone completely free-style. The Accumount scope rings are also not too good, as they do not have the rounded profile. I accept that it is diabolical to get that round profile for the home machinist, but easy enough on an industrial NC machine. Attempting to rectify the Accumounts product is also fraught, as they have used extremely hard steel that resists every attempt to put even a scratch on them.

So I am not defending the mount design or the HEnsoldt scope per se, but I can at least see why they did what they did on 'optimising' the German Hensoldt Dialyt overbore claw mount scope given the mindset they were in.

Having a look at TBSp.73, IDS mentions the CISA decision process in favour of the Hensoldt scope, but the SAC minutes (that I don't have) probably tell us a lot more. IDS also makes the same mistake(??) as me in assuming the Hensoldt scope was on a captured German rig, but he does go on to elaborate to remove doubt that it was indeed a German rifle:

"in mid 1917, a captured German sniper rifle with a light Hensoldt telescopic sight on detachable crawfoot mounts became the inspiration for the assembly of a Pattern 1914 sniper rifle, upon which was mounted an Aldis telescope in the overhead position, using similar mounts. This combination rooved successful enough to warrant its being sent to France for assessment trials, along with the German rifle".

Showing my ignorance again, the SAC minutes talk about the Hensoldt scope being on a "short rifle" (which I assumed to be a Kar98a), but further references to "short rifle" left me under the impression they were talking about the SMLE (vs the MLE/CLLE). The Hensoldt Dialyt 3X being small and light would certainly be well proportioned for the Kar 98a. Can any further light be shed on this?

[Roger Payne]

Lmg15: If you mean the first paragraph of Minute No21 I took it that it was referring to a German Hensoldt scope that had been fitted to a SMLE, as the passage states that the scope (at least I assume the writer meant that it was just the scope) was brought back from France by him, that it retained its original upper mounts, but that the lower mounts were specifically manufactured to suit. Also, I thought that the reference to 'a short rifle' to which was attached 'a light German telescope', suggests to me that only the telescope was German, although I admit there is a certain element of interpretation....

Concerning the prism adjustment, I agree that it is not the kind of thing to be undertaken under trying conditions, but I doubt that was ever intended anyway. It isn't directly comparable with the deflection drum of a modern scope, or even of the No32 twenty five years later. The prism is not ideal, but it was I think representative of one of the more innovative optical technological developments of the time.

I am afraid I know little of the Accumounts No3 (T) mounts other than the fact that the company makes & markets them, although I did gather that they are only approximations to the originals.

[lmg15]

Roger, yes I agree with your interpretation of the SAC minute 21 as contained in your post, but wondering what happened between that and IDS's detailed description of a captured German rifle and the comparative trials between it and the prototype P14T. Some potential cross treading in all of that. I will see what Ian can tell me about it. ATB, D.

[Roger Payne]

Thanks. Ah yes, agreed. There is a crucial gap in the story - why did the CISA/SAC do an about turn on the prism modified Aldis in favour of the Model 1918? Perhaps the German rifle gave the nudge. Please do let us know if Ian has anything illuminating to shed on the story!

Following on from the adoption of the Model 1918 scope instead of the prism modified Aldis scopes for the upcoming P'14 sniper's rifles, was the serendipitous availability of up to 750 of these same Aldis scopes. I wonder at what stage the decision was made to fit them (or some of them) on suitably adjusted claw mounts over bore on SMLE's? It would seem that the PPCo set them up at around the same time (or possibly immediately after) the P'14's. Another gap in our knowledge, unless someone is in a position to fill it??

[Surpmil]

Given their apparent lack of prior history, and failure to deliver the goods leading to govt. take-over, I doubt PPCo. had much if any hand in design and/or concern with interchangeability. It reads more like a company that was set up to bid for war work by parties unknown. Old directories for the area might give an indication of their corporate lifespan. I suspect they simply worked from whatever specs they were given. Their problems may have been due in part to problems hiring or retaining workers skilled enough to produce the product; being in North London there would have been dozens of firms competing for labour nearby during the war. The firms that were in smaller or more distant towns could hold onto their workers more easily - and of course had a core workforce from before the war, and expected to keep going after the war.

It is rather extraordinary to say the least that 500-750 or more Aldis scopes No2/3 were on hand unused in 1917 (if that is the correct reading) out of a total production of about 4000 for the No.2 and No.3 models. That in itself indicates a low priority being given to conversion or some inability to get hold of the rifles, or rifles of sufficient quality. Reminds me of the curious accumulation of unused No32 scopes in 1941-43!

There's plenty of evidence that scoped rifles were always in short supply in France, so some blundering was presumably going on there. Tangentially to that, the letter from Ken Dance, ex-BEF sniper reproduced in TBS (courtesy of Roger Cleverley), states that he and his fellows were told their rifles were specially selected as "one in three thousand".

As for convex rings, they were made AFAIK, by turning the external profile on a lathe and then milling/sawing off two opposing sides to whatever ring width was wanted, the piece could then be held in a vise and the claws etc. be cut in. Accumounts could have done all that on a CNC so can't see why they didn't -cost?

Going back to those contract lists posted above, we have the mystery of the Bartle mounts, which given the large number quoted, should be a common survivor(?) The fact that they aren't might mean something went wrong with either the design or the company, as per PPCo. and the contract was never completed? Could that be the reason for the large accumulation of No.2 & 3 (or just No.3?) scopes, which certainly should never have occurred.

[Roger Payne]

In truth there are so many questions that can be asked about WW1 designs & production, but I have fired a couple at IDS to see if he has any comments to make. Specifically, if he has any ideas about the Mk VI graduated range drums on some scopes, & also if he can shed any light on the decision to abandon the Aldis in favour of the Model 1918, although I have limited it to that as I know another of us was also contemplating asking him about certain aspects of the various discussions that we have had in this thread. I've received an acknowledgement but nothing more as yet, incidentally. When I do I'll let everybody know......

Meantime surpmil, you've given me the impetus to dig out my copy of Sambrook's 'The Optical Munitions Industry in Great Britain, 1888 - 1923', & there is some interesting stuff therein, although it does not answer anywhere near all of the gaps in our knowledge. For instance, he describes an attempt in 1914 by Barr & Stroud, to lure away skilled workers from the Periscopic Prism Company, with whom B&S had dealt since 1911, which if nothing else shows PPCo were not specifically set up at the outset of the Great War, but had already been in existence for a few years at least. He says that the attempt was not successful, by the way!
One or two other snippets he comes out with; the 1st Pattern Aldis was accepted in January 1915 & 200 produced by July 1915, but by summer problems with the range drum keeping its settings, & with fogging due to humidity, led to a redesign resulting in the 2nd Pattern, which was accepted in November 1915. Thus far unfortunately I've not been able to find anything specifically dealing with the 3rd Pattern & prism addition.

Back to the PPCo scope & a total of 'over 4,400' produced by April 1917, with production continuing until the end of the war. Quite possible, although the total of PPCo equipments produced was slightly less than 5000, so production must have slowed down rather over the last eighteen months of the war. And admittedly few original rifles survive, but odd that nobody seems to be aware of any dated 1917 or 1918..........though perhaps I've answered my own question, if the rate of production did indeed slow down appreciably!

Sambrook also confirms that by the end of the war the PPCo were under state control.

He doesn't go into detail, explaining why the Aldis was replaced by the Model 1918 plagiarised & slightly modified from the Hensoldt scope, but he does say: 'The War Office's eventual decision to replace both types (Aldis & earlier type PPCo scope) with one copied from a German riflescope stemmed not from any crucial functional failure in what was available, but more from a supposition that the proposed alternative was fundamentally superior in design & so capable of better standards of performance.' Unfortunately he doesn't tell us how the War Office went about their decision making!

Although the section on rifle scopes is brief, it makes interesting reading.

[lmg15]

Surpmil, good point about whether PPCo actually designed the Patt 18 claw mount, or whether they just made them. I thought of going back to TBS and seeing whether there was a signature block that would indicate the designer, but alas, they are just the AID drawings which include the Aldis scopes as well. However, the hint is in the title "Enfield Overhead Fittings for Rifle, Magazine, .303 inch, Patt 1914. So your suspicions would appear to be correct in saying a Government design made at the PPC factory site.

Regarding the finer points of scope ring design, I pondered how I would go about making the convex shape. I did think of the method you refer to, where you essentially turn up something resembling a towball on the lathe, then slice / mill and drill accordingly. This is the way at least one of the WW2 German ring sets was made. However, measuring it up, the radius of the convex shape is much larger than the radius of the rings themselves. You also have the problem of the rear leg being an unsymmetrical shape, and then having to shape the integral clamping lugs at the top just to complicate the process further. All I can see for the average home workshop punter is a lot of fiddling around with a file, that would not come out looking like a bought one. So methinks there is some dedicated machinery involved, possibly of the copy mill / pantograph type, and special concave end mills, etc.

Surpmil and Roger, some very illuminating info on PPCo and the British optical munitions industry - many thanks. D.

[Roger Payne]

Thanks lmg15, you have considerable insight into the manufacturing side of things! In fact, when I got the Aldis over bore claw mounts made about six or seven years ago the machine shop managed to make them with the radius, but even so had to make the clamping lugs as separate pieces & braze them in, something that the original manufacturers managed to avoid, albeit a century ago. Nonetheless, all way beyond my rudimentary abilities....