Interesting Youtube video of homemade caps

Google translation:

Quote :

Commentary stuffing the money to cap resin Cart

Ochi with gunpowder is cheap, but that becomes higher than MG cap and align the material.
You can be reused several times wheel of rubber, but I wonder if given the time and effort.

I'd say a thicker piece of rubber would be better, as the thin piece in the video has the possibility to wobble out of place once pushed to the rear.