No. 32 Mk.III construction/design question

[gravityfan]

Hi All,

I posted this on the Jouster forum, but I am advised that Mr. Laidler, for one, is active in this forum rather than the old one; so if it's OK with everyone, I'd like to copy it here:

Yesterday at the range, I was asked a question that not only could I not answer, but had never occurred to me to ponder.

Does the distance between the cross-wire and the tip of the pointer represent some specific distance in use, or is it a design/construction parameter?

It appears to me to represent about 9" at 100 yards. That would make it almost exactly centre mass of an average Hun at 500 yards, but I cannot think that could be the answer.

Does anyone think it represents some useful measurement? Any reason why it would be designed that way if not for use in the field?

Cheers.

Information

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[Peter Laidler]

Good question and I'll have to look at the technical spec during next week BUT offhand, I don't think that the distance you mention is relevant as I have seen them differ greatly. Another problem is that while the grat is .006" (I have noticed that some are slightly thicker, at .0068") and the X wire is .001" (....although the L1A1 spec says that it is .0008"....) this is the simple bit. The HARD bit would be getting a constant distance between the tip of the pointer and the crosswire because due to the magnification of the two plossl cells (the erector and the ocular don't forget....) the actual size of the grat is magnified x25 or x27 or so I seem to remember but feel free to correct me if I'm wrong.....

Knowing this magnification, it'd be virtually impossible to get a constant distance you speak of.

However, you can use the grat to approximately judge width and height by knowing the obscuration factor (that is the width the grat covers at X yards). The sniper courses used to use this to guestimate things on the old courses, with L42's/L1A1's and the early L96 S&B scopes but the new ones (the big x4 to 12 scopes) don't cater for these little wheezes

It's getting into the optically complicated now and my optical engineering tutor from uni days, the kindly Mrs Macintyre said to me during a tutorial once '...try not to be an optician in later life Peter.....'

[gravityfan]

Thanks for that interesting input. Fascinating to hear how magnified the graticle is, I would never have realised that.

From what you say about the distances and sizes being so hard to control, was the over-riding requirement just that the tip of the point be in the centre of the image?

Cheers.

[Peter Laidler]

Yes, that's correct Gravityfan. In the clinical world of big Base workshops, the tip of the grat must fall in the centre of the image window with the range and def. set at '0' This would seem to be a bit of a paradox because shooting thereafter, you're only using the lower half of the image (yes, 0 to 10 LOWERS the point to lift the muzzle don't forget.....) And the closer you get to the edges of the image screen, the greater the optical aberration but that's the way it is! But to be fair, if the point is in the centre of the screen when at 0, then 10 is still well within the well defined, distortion free area of the screen

In the real world of Armourers shops and snipers, then it changes slightly but even then, it won't be many clicks out from centre.

I've mentioned this before but I've seen rifles with scopes that are zeroed with the point of the grat all over the place and they insist that it's all original and matching and used by their dad on D-day............

Interesting thread and good question Gravity. Made me think a bit, scratch my head and trawl through my old notes I can tell you! Phew!

While talking of snipers, it's absolutely bucketing down with rain on Salisbury plain and has been for a day or so now, The snipers are still out there! I hope they're all holed up well and dry. I suggest that they warm up a pack of that corned beef hash in their ration pack before they cover the attack this evening

[Badger]

I'm not sure if this is exactly what you're looking for, but there's an entry in the England Section (click here) of the MKL (Milsurp Knowledge Library), showing the dimensions of the No.32 scope, including the measurements of the cross wires etc.

(Click PIC to Enlarge)

1952 Instructional Pamphlet for No.4 Mk1(T) sniper rifle (click here)

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Regards,
Badger