Its not a percussion fuse, Tom, but rather a concussion fuse.
It had a glass vial of liquid fulminate surrounded by lead shot. The vial was intended to break upon firing. Then on impact the exposed fulminate got exploded by the loose shot inside the fuse.
In sum, this type of fuse did not have to hit direct on to force a slider into an anvil cap. The "concussion" of impact was sufficient to set it off.
