1917 french signal flare pistol flares


1" is 25.4mm, not 26.5mm.

Medicbob, where are you located?

I just remembered, (yea, not enough sleep the past few days), I have 5 1" flares, (although I am currently unsure where I stashed them).
I would not shoot them, but if you want one for fitting and display only, I can be talked into sending you one, (once I find them again!).


1" is indeed 25.4mm but all the British flare cartridges are listed as 1" and later alloy cases are also marked 1" 26.5mm. Never seen British one marked 25.4mm.
We are being too technical here but thanks for your input.


Here is a photo of the common later alloy cases showing the 1" & 26.5mm size.
The rim is 30.2mm wide and must be reduced to 28.4mm to close the barrel on a French signal pistol and fit the chamber.


I wonder why, because 26.5mm flares would not chamber in a 1" flare gun, and the 25mm flares I had [have? somewhere?] would not chamber in my 26.5 mm flare guns, because they had a larger base just above the rim.
Those 1" I posted above have a slightly larger base with a shallow shoulder. I need to dig them out!
Weirder and stranger…


We are straying from the original French question.
Your M73 flares fit the British 1" pistols and the H&R MkV1 OK but the rim is too thick to close on a 25mm US Mk1V due to the thick rim. Some USA pistols are strange undersizes. They only chamber the alloy USA cases, not British ones.
1 1/2" M8 and M9 (I think) hand launchers do take British cases.
Too detailed and getting off topic. Cheers. Ron.


Hello Ron,
Sorry for the delay.
I arrived from Asia two weeks ago and i am leaving again in 3 weeks.
Therefore just time to unpack, repack and take care of the usual boring administration paperwork.

I checked quickly my general notes, not searching deeply the drawings of ctges and chambers.

During WWI the french flare pistols were designed to fit the sfm standard for the ctges.
The dimensions for the chamber are :
Max rim thickness : 1.90
max rim diameter : 28.70
max rear diameter: 26.70

And the british flares must fit in a chamber with the following dilensions
Max rim thickness : 3.30
max rim diameter : 30.50
max rear diameter: 27.70

Therefore you are right, a foreign flare will not fit into a french wwi flare gun, except if you reduce the rim diameter of the ctges.

Most of the counties after WWI used the British standard for their flares and all the modern production is also at this standard.

Therefore I think the french flare pistols we found in quantity 30 or 40 years ago on the market had the chamber altered to fit the common flare ctges.
(the difference in tube diameter being of small importance due to the lack of pressure)

Sorry for the delay.



Thank you for the reply and chamber dimensions. I have not seen a French pistol that takes British ones but yes, it is possible to alter the rim dimension of the chamber. I hope you enjoy your travels. Till our next conversation. Ron.


i come back after the 20 th of April.
Because I have no memory just send me a quick note and I will try to find you dmensions about chamber dimensions.

I have a question : Did you find a document (CIP, SAAMI or other) giving the nowadays dimensions of the chamber and ctge and the maximum pressure .



You have given me the dimensions of chambers. I do not have documents on pressures etc. I do not go into such detail. I only collect flares and pistols.


I finally found my Olin Corp 25mm flare cartridges, (but I cannot find my 1950s’ U.S. 1" cartridges to measure), to make a comparison to a “standard” 26.5mm flare cartridge, 26.5 on left, 25 on right.