It's not really a timer. Typically a cannon round would simply have a slow burning fuse from the base of the shell to the explosive inside. The fuse was ignited on firing and would eventually burn through to the charge at a time interval equal to the maximum effective range. A tracer composition could act as this fuse.
Wikipedia lists 4 types of ammo for the 25mm, one of which is "high explosive tracer self destroying". No idea about the other three. So self destroying was at least an option.
Look at time 2:43 for a sky full of little white puffs at a set range. The video is also big on hats AND helmets! Looks to me that hats were used during firing practice and helmets when there was real work to be done.
Last edited by Hooston; 06-27-23 at 04:23 AM.
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