"Sighting telescope No.30"

All, can anyone provide me with any information on this???

What type of sight it was...I'm assuming for tank gun work given where I found it - on BOTH guns, 2pdr and 3in howitzer - on the Churchill MkI?

What the gunner's eye saw - was it a simple crosshair or was there a graticule for indirect fire?

 

No, as I cant see anything or catch sight off.

Is a photo missing ?

 

Oops, no there's isn't a pic! I was looking for detail on the armament of the MkI Churchill and what it was used for, and picked up a download of the instruction book for the tank for the ammo loadout for the 3in howitzer...

...THEN saw that both weapons had what I presume is a "direct fire" telescope???

Does this mean the MkI's howitzer was restricted to direct fire? I know it had very little elevation cos of the installtion in the front glacis...

 

According to a thread on HMVF, THIS is the view through a No.33 Telescope, the simplfied version of the No. 30...



But what do the three figures on the left mean underneath "GUN" - the 5, 10, and 15? Degrees of depression, or approximate ranges in hundreds of yards?

 

I know you were looking for "Sighting Telescope No 30", and looking at this 'spares/stowage list (http://www.armourinfocus.co.uk/a22/stowage/mk1list.htm) it shows Nos 30 and 33. On searching further I found a discussion for the telescope 33 (http://www.warrelics.eu/forum/equipment-field-gear/telescope-sighting-25853/) which mentions that this was "The No.33 mk.IIs was SPECIFICALLY designed for the 2Pdr.x BESA (7.92mm) combination of armanent"

So logically from the above the telescope 30 would probably have been for the howitzer.

I am no expert at all in these fields so I may be totally wrong, I was trying to work it backwards - if you understand that

TD

 

Hi TD, I saw that armourinfocus page just after getting hold of my download...

The manual I got was visibly for a "MkI early", pre the Rebuild programme; some illustrations show the early-type air intakes

I would assume that the armourinfocus mention of the No.33 sight as an alternative there is because when supplies of the 3in howitzer ran short they fitted a Besa MG in its place....coming up with the Churchill MkII! Basically identical to the MkI apart from that.

The reason I went lookng in the first place is that I'm chasing down data on "CS" Close Support tanks...and among other issues with them was a reputation for poor accuracy....now that I've got all the above new information I can understand that there WOULD have been some MAJOR accuracy issues using the same type of direct fire sighting telescope for a high-velocity tank gun as for a very low velocity howitzer! How would a sight designed for the 2-pdr be supposed to deal with a lobbing arc of fire, windage etc...???

Especially in the Churchill MkI, where the hull fitment of the howitzer resulted in limited elevation anyway!

Now I just have to find out what sights were used on the SAME weapon, the QF 3in howitzer, in the Matilda II CS, the Tetrarch CS, the Crusader CS...!

I know all the aboves' gun tanks used No.30 telescopes...just have to find information on the howitzer installation in the CS versions.

 

Just trawling around the internet, hoping this might be useful (say so if it isn't) I found some basic pieces of info on the different munitions:

http://en.wikipedia.org/wiki/Ordnance_QF_3_inch_howitzer
Calibre: 3 inches (76 mm)
Length of barrel: 75 inches (1,900 mm) (25 calibres)
Overall length: 78.2 inches (1,990 mm)
Weight: 256 pounds (116 kg)
Muzzle velocity: 600 to 700 feet per second (180 to 210 m/s)
Ammunition
Cartridge: 76.2x134R
Smoke: 13.4 pounds (6.1 kg)
HE: 13.9 pounds (6.3 kg)
Range 2,000 to 2,500 yards (1,800 to 2,300 m)

http://en.wikipedia.org/wiki/Ordnance_QF_2-pounder

Shell 40×304 mm. R
Calibre 40 mm (1.575 in)
Breech semi-automatic vertical block
Recoil hydrospring
Carriage three-leg platform
Elevation -13° to +15°
Traverse 360°
Rate of fire 22 rounds per minute
Muzzle velocity 792 m/s (2,600 ft/s) with AP shot
Effective firing range 914 m (1,000 yd)
Maximum firing range 1000 m (1093.6 yd)[1]
Feed system Breech-loaded
Sights No.24b

I was interested to see the muzzle velocities are in fact 'similar' but the difference in 'range' surprised me. Heres hoping some of the veterans may well be able to help you in your quest.

TD

 

TD, they're actually not - the two contributors have formatted the data differently, a common issue with Wiki - look again...

In feet per second terms - 600-700 fps vs. 2,600 fps! - the 2pdr is c.four times higher than the 3in howitzer!

Hence the question over using the SAME sight for both...the 2-pdr will of course have the much flatter trajectory of a direct-fire a/t gun....

 

Hi phylo

I really must stop trawling late at night - thanks for correcting me and my mental breakdown on units of m/s v's ft/s

TD

 

Regarding the sights, the Churchill I is the worst example as the 3" howitzer was mounted independently. The sights for the turret-mounted CS weapons would be the interesting ones to see as there must have been a big divergence between the range markings for the gun and the Besa. The restricted field of view of the telescopes was probably the practical limit on range - I imagine the target dropped out of the field of view long before maximum range was achieved.

An advantage of a single sight for a coaxially-mounted 2 Pr and 7.92mm Besa is that their muzzle velocites are very close, which explains the similarity of the range markings (hundreds of yards) in your, er, sight picture picture. The velocity of the much lighter Besa bullets would have dropped off more quickly than the 2 Pr shot, hence the significantly shorter range.

Anyway, you may find this link useful: British Sighting Telescopes

I don't believe there was ever any intention that the CS weapons were intended for indirect fire. Discounting the commander spotting for the gunner, the practical limit on range would be the field of view of the scope. I imagine the target would drop out of the bottom of the sight long before maximum range was achieved.

 

Telescopes are by definition for direct fire, but you can use them for indirect if there are horizontal graticules, obviously you don't get much azimuth from the aiming point. Equally obviously you need a sight clinometer for elevation, and also equally obvious, a plane surface on the ordnance to put it on when laying. Some might be surprised to learn that this is the current back-up laying method for AS90 155mm if the electronic sights fail.

Presumably the numbers marked on the graticule going up as they get lower down are ranges, 500, 1000, 1500 yards, ie you need to cock the barrel up as range increases. This of course is why there are so many different Telescopes, basically you need a different one for each ordnance/ammo combo, less those graduated for mixed types. Although for high MVs and short ranges you may get a certain amount of one size fits all.

 

Hi Mapshooter and Idler...well, short ranges were all you got with the 3in and 3.7in howitzers! The absolute maximum range was on or around 2,000 yards...and I`ve seen "effective" ranges listed as low as 1,000 yards...

I`ve posted up a query on HMVF asking if any of the guys there know the sight types for "regular" CS tank types...so same query here; does anyone know? Logically it would have been the same item for all the CS howitzer tanks that normally had 2pdrs...?

 

Mapshooter, I'm back at my decent PC, so just got a chance to cut&paste properly...

So how on earth was the SAME telescope going to work for a flat-trajectory anti-tank gun and for a high-angle, "lobbing" howitzer??? Or is the answer just..."badly"?

 

I've been trying to find a ballistics calculator to get approximate effective ranges for 15/25lb (3"/3.7") projectiles at ~200m/s at 10° elevation (half the FOV of a no. 30 scope). No joy yet...

 

The telescope was only used to lay in azimuth, hence the need for a clino and a plane surface on the ordnance for laying in elevation. The latter was probably also needed for sight testing, although the clino for this was probably held by EME. Simples really as the meerkats say.

Ballistic data comes from range and accuracy firings, this was used to calculate the data that went into the range tables and engraved onto sighting scales. The aeroballistic data required by computers running a modified point mass or similar model was not produced in WW2, bit of a surprise that, they obviously couldn't see into the future, fancy not realising that digital computers were coming down the track, I'd call that a national scandal. That said it may be possible to take the RT data, derive polynomials and use a program of the type developed by Zengrange for AFDC (a repackaged handheld calculator). Of course if you have RTs they will give you all the range & elevations.

 

Any luck with that, yet? It sounds like it would be a vast improvement on anything I could contribute; I can be a bit of a plank sometimes.

 

Did they even produce RTs for tank guns?

 

duplicated post

 

Mapshooter old chap, phyloroadking has asked very similar questions on two other threads. I made my efforts to answer the question of how one might lay a howitzer without sights, (based on practical experience with an M109 battery as BATUS Suffield in my youth on post) #15 of the OTHER 3" and 3.7" Howitzer thread he started.. http://ww2talk.com/forums/topic/52013-3in-and-37in-cs-tank-howitzers/ Someone must have produced a range tables for the 3.7""Mortar" during the development and testing of the weapon. However, whether any were produced and circulated within units is a different matter. (Could the average tankie have made any use of range tables? Were they any practical use in a tank which would not be on a level gun platform. In any event after the first round the gunner or commander could corrects as per a small arm. Bovington is the place to check. Firepower might have a copy. I am not sure how much

 

Half-way there and saved some effort: Fletcher's Mr Churchill's Tank has this to say on the subject of the Churchill I's hull-mounted 3" howitzer:

But is that 'range scale' the graticule in the sight (the No.31, according to the wwiiequipment table), or a gadget that real Gunners might recognise?

The comment about HE>Smoke is certainly consistent with the doctrinal differences between the infantry and cruiser tank schools, and provides a logical reason (though maybe not a compelling one) for why they developed the 3" as an alternative to the 3.7".