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US Documents on British Trench Mortars


RodB
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I've been reading Some 1917 and later US manuals which describe details of British trench mortars. While mosts details agree with what I've found elsewhere, some numbers appear odd :-

2 inch mortar bomb is reported in several places as weighing 52 lbs. All other sources say 60. Yet photos I've seen of the ease with which British troops carry 2, one with each hand, make it look closer to 50 than 60.

Maximum range of the British 9.45 inch mortar is quoted as 1140 yards with a 152 lb bomb. All other sources quote 2265 - 2400 yds. This short range matches figures I have for the original French 240 mm CT, but it fired a massive bomb and could be excused for having a short range. The British apparently started out with the CT but cut the bomb weight down from 180 lb (192 ?) to 150 (152 ?) lbs and hence gained range. So have the US writers garbled the data ?

Maximum range of the Stokes mortar is quoted in 2 separate US manuals as 430 yards. Brit sources quote 1200.

I also found some strange numbers in a US Army reprint of the British "Artillery in Offensive Operations" of Jan 1917 about how many bombs/shells were required to accomplish tasks. 5 of the 2 inch bomb were quoted as necessary to destroy a yard of trench, versus 3 9.2 inch howitzer shells. MG emplacement with roof consisting of 3 rows of pit props : 80 2 inch, 50 9.2. Am I missing something here ? Yet a separate British document "Counter-Battery Work", also reprinted by the US Army, quotes 60 9.2 rounds necessary to destroy a single well-protected gun pit. Are there some extra zeroes appearing here ? I would have thought 60 9.2 rounds would obliterate the whole neighbourhood.

I'm confused. I'm arranging to get the AWM to dig out their manuals for all the mortars so I can visit and hopefully photocopy the details. But I find it odd that the US military would get such details wrong.

cheers

Rod

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Rod

I have a copy of the Range Tables for the 3 in Stokes Mortar Printed in September 1917. This is not a good copy I have transcribed to main body of the Range Table.

The front cover has (PROVISIONAL) RANGE TABLE FOR 3-INCH STOKES MORTAR

(Cartridge, 95 grains ballistite, reinforced with

Charges (5 grains, guncotton yarn

( Rings, 110 grains, .3 mm flake cordite

Projectile - Bomb, weighted 10 lb. 11 oz

Transcribed main body of Range Table.

Stokes_Mortar_Range_Tables.doc

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Thanks for providing that John. Looks like range for the Stokes mortar was 800 yards max with all 4 propellant rings. Could it be that the US figures of 430 yards quoted are for only 1 propellant ring, either through some transcription error leaving out the ranges for rings 2 - 4 but... The US Jan 1918 manual states : "Two sizes of cartridge are issued for use with shell viz. Green cases 190 -300 yards. Red cases 270 - 430 yards". Sounds inadequate. But I've found reference elswhere to a US Blue cartridge. The missing maximum range cartridge, not available when the Manual was issued ?

Rod

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One should never rule out typographical errors. The people who were preparing the US version of the manual, after all, had probably never seen a trench mortar, and would not have spotted errors of the sort mentioned.

That said, there are other explanations for the differences in weights. The first that comes to mind is different models of bombs, particularly where the material used in the body of the projectile are concerned. The heavier bomb might well have been one with a cast-iron body, while the lighter one might have had a body made of steel.

As for the figures for the destruction of a given emplacement, the fact that the total weight of mortar projectiles needed to destroy a very small point target was smaller than the total weight of 9.2-inch howitzer projectiles needed to do the same job may be a reflection of greater inherent accuracy of mortars firing a very short ranges. That is to say, where certain point targets were concerned, a direct hit by a relatively small mortar bomb may well have been as effective than a miss by a (very large) 9.2-inch shell.

By the way, when fired a short ranges, Stokes-type mortars could be very accurate. When I was a young Marine in the late 1970s, I would often hear tales of skilled mortarmen who could regularly place a bomb from an M2 60mm mortar (which was an American copy of the Thompson-Brandt modification of the original Stokes) into a 30-gallon rubbish bin.

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  • 2 months later...

Rod,

The US document is probably quoting an earlier reference.

The Handbook for Stokes Trench Mortar, 3", Mark I, Issued by the General Staff in 1916 gives the maximum range as 430 yards.

Charge - 175 Grains Ballistite (Red Cartridge)

elevation 43.5 degrees.

Range 430 yards

Time of Flight 10.2 seconds

Chris Henschke

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There were at least 4 different models of the 240 mmm mortar in the French Service. An American Handbook I down loaded appears to be based on the French 240 rather than the British 9.45 so perahps these figures are for onr of the French series.

Does the material you accessed specifically say Stokes 3 inch? The Americans also used the Stokes 4 inch for chemical and gas rounds.

Re the 2 inch toffee apples. There were also toffee apples fired from the Vickers Trench Howitzer They were smaller and lighter that the 2 in mortar round but esentially the same shape. Also there were chemical (smoke) and gas rounds for the 2 inch these may have been of a different weight

Ample scope for confusion somewhere!

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Yes, it does say specifically 3 inch Stokes. It is exactly as I have written it. The Handbook for Stokes Trench Mortar, 3", Mark I.

That is the title of the publication I am quoting.

Here is the table.

post-671-1200924651.jpg

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I've been reading Some 1917 and later US manuals which describe details of British trench mortars. While mosts details agree with what I've found elsewhere, some numbers appear odd :-

2 inch mortar bomb is reported in several places as weighing 52 lbs. All other sources say 60. Yet photos I've seen of the ease with which British troops carry 2, one with each hand, make it look closer to 50 than 60.

Maximum range of the British 9.45 inch mortar is quoted as 1140 yards with a 152 lb bomb. All other sources quote 2265 - 2400 yds. This short range matches figures I have for the original French 240 mm CT, but it fired a massive bomb and could be excused for having a short range. The British apparently started out with the CT but cut the bomb weight down from 180 lb (192 ?) to 150 (152 ?) lbs and hence gained range. So have the US writers garbled the data ?

Maximum range of the Stokes mortar is quoted in 2 separate US manuals as 430 yards. Brit sources quote 1200.

I also found some strange numbers in a US Army reprint of the British "Artillery in Offensive Operations" of Jan 1917 about how many bombs/shells were required to accomplish tasks. 5 of the 2 inch bomb were quoted as necessary to destroy a yard of trench, versus 3 9.2 inch howitzer shells. MG emplacement with roof consisting of 3 rows of pit props : 80 2 inch, 50 9.2. Am I missing something here ? Yet a separate British document "Counter-Battery Work", also reprinted by the US Army, quotes 60 9.2 rounds necessary to destroy a single well-protected gun pit. Are there some extra zeroes appearing here ? I would have thought 60 9.2 rounds would obliterate the whole neighbourhood.

I'm confused. I'm arranging to get the AWM to dig out their manuals for all the mortars so I can visit and hopefully photocopy the details. But I find it odd that the US military would get such details wrong.

cheers

Rod

Rod,

I wonder if some (if not all) of the discrepancy relates to the fact that 'Imperial' weights and measures are not the same in every respect as 'American' weights and measures that use the same nomenclature?

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