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RodB

Stokes Mortar calibre - actually 81 mm ?

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Does anybody know what the actual bore diameter of the "3 inch" Stokes mortar was ? Reason I ask is that the AWM Stokes bomb exhibit is described as being 81 mm diameter. ??

thanks

Rod

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The tables in Hoggs Mortars gives the Stokes "3 inch " as being of 76mm. 81 mm was the common caliber of the post war Brandt series of mortars which led to many designs over the years including the current LS. Are you sure its really a Stokes?

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The tables in Hoggs Mortars gives the Stokes "3 inch " as being of 76mm. 81 mm was the common caliber of the post war Brandt series of mortars which led to many designs over the years including the current LS. Are you sure its really a Stokes?

I can only quote the AWM caption :

"Maker: CA Vandervell & Co.

Date made: 1916.

Steel; 3 inch Stokes mortar inert high explosive projectile. The mortar projectile is a steel tube shaped canister with a detonator and firing cartridge holder at the rear end and a fuze mechanism at the front end. The cartridge holder has gas vent holes along the body. The projectile is painted khaki and there is a red and green filling ring painted around the body.

Markings - projectile - CAV (BROAD ARROW); 10.16; JXB H/I (BROAD ARROW); Fuze - NO 146 MK 1 FUZE.

Measurements: Projectile diameter: 81 (mm); Projectile length: 417 (mm); Projectile weight: 4.1 (kg)

Summary: The 3 inch Stokes Mortar high explosive projectile was introduced into British Army service in 1916 and remained in service on the Western Front for the duration of the First World War. This mortar bomb is inert and has been marked 'FREE FROM EXPLOSIVES'."

800px-3inchStokesHERound.JPG

Rod

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Well it certainly looks like a Stokes round. One can only assume that

a] some one at the AWM mis measured the round, or

b] some got lazy and just assumed that the Stokes followed the international standard (first established by Brandt just after WW1) of 81mm applied to the Stokes and never bothered to measure it.

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Rod

I have just put a caliper on the unfired Stokes bomb head beside me on my desk and, guess what, it is 81mm in diameter. Looks like the compiler of the table used in Hogg was the one who made the assumption regarding diameter, and for convenience of terminology the designation 3" was used as the closest round figure in Imperial measure - after all we talk about the 18 pounder gun when its shrapnel shell weight (its original ammunition) was actually 18lb 8oz.

Come on, there must be plenty of you out there with Stokes rounds to measure to either confirm or confound the 81mm used by the AWM caption writer.

Mike

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Strange because he got the 4 in one spot on (its actually 107mm or 4.2 inch)

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I find a whole range of sources that give the calibre as 76.2mm. However I note that Brandt's 81.2 mm mortar was originally referred to as the Stokes Brandt mortar and in some places was simply called a Stokes mortar. A very large number were sold or made under license. Could the rounds be for one of these?

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9d61d311.jpg

These 3 are made by two different companies but are the same size,ie.81 mil dia for the base & head caps but,3"(76.2?) dia for the 'tube' section.

61be1aad.jpg

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Hi Pals. I assume the smaller mortar is a Stokes. Anyone know what the other one is?

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Hi John,

both seem to be Stokes,the larger is the 4" that mr.Centurion was talking about.

The black 'blob' on the base could be the propulsion charge,a powder bag ignited by the shotgun type cartridge set in the base(look at my foto & see the holes in the base?).Not sure.

There's a good chance that your one there was a gas round but I dont know how I could prove that from here.

I'll see if I can dig out a photo.

Dave.

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It is a 4" Stokes used by the RE Special Brigade for chemical or smoke.

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Found a couple,not the best but they give you a general idea...

fa6de4ad.jpg

ee2b5515.jpg

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Well you live and learn - but why do so many different sources list 76mm?

BTW a mint round from a US web military web site.

Stokes1,Stokes 2

BTW 2 a number of US museums have Stokes Brandt mortars C 1927 labeled as Stokes Mortars!

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Thanks Dave & Simon. The shotgun type cartridge was unfired so I didn't get too close! Wimp but still alive..................

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I think the answer might be that an author does a quick conversion of 3" and quite reasonably comes up with 76mm. If enough authors see that and accept his word, it becomes part of the stuff that everyone knows. Who is going to go out, find a few rounds and measure them? Some geezer on GWF, that's who!

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b] some got lazy and just assumed that the Stokes followed the international standard (first established by Brandt just after WW1) of 81mm applied to the Stokes and never bothered to measure it.

Well,I think your 100% spot on there.

Seems to answer a lot of questions but,will we ever know for sure?

Dave.

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Thanks for clearing that up gentlemen, and for posting the photos. I've gone in and applied the 81 mm figure to the Wikipedia article. Sounds like the WWI "4 inch" mortar was actually 4.2 inch then, which accounts for the later 4.2 inch designation ?

regards

Rod

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Hello all,

Yes 81mm for the bomb, the bomb is not a tight fit in the barrel in order to allow for windage ie the difference in diameter between the bore and the shot.

Up until about 18 months ago I had a complete Stokes gun and a lot of the accessories. Due to a major shift in my collecting interests (I now collect and run WW2 armoured vehicles) I sold mine to the National Army Museum.

The gun is interesting in that it was recovered from the Somme battlefield, when the ring road was constructed around Albert. The assumption is that it was abandoned during the March retreat as when found it was complete with a stock of rounds and still had its firing pin in place.

I had to carry out very little repair to the gun other than to straighten the bipod legs which were rather battered (and might account for its loss) and the replacement of the elevation and traversing threads. More than 95% of the original nuts and bolts were reused as the whole thing was in remarkable condition. I subsequently replace the barrel for a much better example (made by the Rover car company in 1917!) which was found in St Pol (site of a TM training school I believe) which was being used as a roller in a small workshop until the 1990's.

Regards

Tocemma

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