Plugging Salute Shells

Hi,

one question for the pyro freaks among you:

Recently i made some flashpowder salutes. I used the cardbord hulls of 15mm whistlers. Looked like what the americans call "M-80".

The trouble was to seal the tube properly.
KClO4 whistlemix or even 70/30 Flash is of course uncritical als it only need a minimum of confinement.

But as I prefere a dull bass over some high-pitched bang, I want to make bigger salutes using KNO3 or Ba(NO3)2 Flash, where strong confinement is required.

I've got lots of nice hard cardbord tube here, 4mm walls
Inner diameter is 27mm.

I want devices with a save operation (unless we can talk about save operation at all)and I dont want the to jerk any concrete or plaster at me.


->I need save plugs. And strong ones, not like these plastic things sometimes delivered with professional pyrotechnical shells.

Maybe this problem sounds familiar to you... Any solutions?

Im considering something like wood sawdust mixed with white wood glue...