Gun Cotton Tufts in Early WW1 .303 Grenade Launching Cartridges explained

Can anyone please explain why all the early WW1 British .303 Grenade Launching Cartridges had a 1 grain tuft of gun cotton, or later a 1.4 grain yarn of guncotton, at either end of the propellant charge? I can’t find anything explaining why in Peter Labbett’s .303 book or in my other reference material. Thanks in advance.

Could we please see a photo of the “yarn of guncotton”?

Sorry I do not have one. I don’t wish to break site rules, but recently inerted a WW1 Grenade Cartridge and found the tuft and wondered what it was. It is detailed in Tony Edward’s web site and Peter Labbett’s book but there is no explanation why.

Experience with the H Mk IV in Australia, without the guncotton tufts, resulted in prematures and tail failures, when using live grenades.
Changing to the addition of the gun cotton tufts eliminated the problem.
My feeling is that the guncotton gave a more consistent burning of the 5-2 cordite. But that is only my thoughts, nothing official.

I’d have to go back through my notes for the headstamp of this round, but I think that this is an example of such a launching blank.


Um…I think I know who bought that 1/2 of a round (or it’s brother ???)

only part of H/S that remains = H (roman numeral “2”

written on case is MK2

my other left side example = R 17 L VII

right (just for giggles) H/S remains = H.1Z

As a Junior in high school back in the mid-1950s, we made tiny quantities of gun cotton in chemistry class. I have no doubt that those tiny tufts would do the intended.job.

Well, I’d have to do some real digging to see if I did a second round. Look at the different cordite (much thinner) in yours.

The round I showed above had a blackened case. Is that the same as the sectioned one you have Poivre?

apologies for not comparing the powder charge…it’s bed time :slight_smile:

if you didn’t cut it…I must be two-timing another “saw guy” :rofl:

H. Mk. I Z for use with rifles fitted with grenade discharger cup.
H. Mk. II for all rodded rifle grenades.

As the rod took up space in the barrel there was considerably less volume available for expansion of the gases when the cartridge was fired from a rifle with a discharger. Thus two different types.

However, with a rodded grenade there is greater space and consequently lower pressure behind the rod compared to a bullet. Thus the guncotton tufts were employed to ensure complete ignition.

That would appear to be the same solution we reloaders have used for the past 45+ years in dealing with reduced powder charges, for gaallery-type smokeless powder loads, and especially with black powder cartridges.

We used a 1 grain by weight tuft of Kapok, (no residue left, and no change to the burning charachtistics of the powder), to keep the powder charge against the flash hole for a consistent burn, and to achieve consistent velocities.

And we thought it was a unique solution that we devised for the problem!

Guncotton is an explosive material Kapok is not so not the same usage, A filler material vs an aid to complete combustion.

Yes, but by the look of those sectioned cartridges, those were reduced powder/cordite charges, so the same theory applies.

Post deleted.

Yes, but in both cases the powder/cordite does not fill the cartridge, note in the right hand cartridge, the wad pushed down to hold the powder against the flash hole, as we did with the Kapok.

No the guncotton is next to the flash holes.
borrowing Paul’s photo.

AND the cotton at the top of the case is there to keep the cordite from moving UP, away from the base of the cartridge, as in reduced powder cartridges, AND in the second sectioned cartridge, (which you continue to ignore), there is NO “gun cotton”, but a wad at the front of the cartridge, in order to keep the powder against the flash hole, which is the standard for reduced powder cartridges.

Does anyone have a sectioned H Mk 4 with rose petal crimp?
.303 MF HIV 2nd P copy