The only real thing wrong with this is that the hammer has a "corrugated" surface, instead of a flat one, so that the caps don't go "BANG!" as much as "Phut!" (if you're lucky). A bit of work with a pair of tinsnips and a tin (empty food tin) results in a strip of metal that can be bent into a sideways-on "L" shape. The tail of the "L" can fit into a space in the casting, the long back of the "L" sits under the hammer, and the caps feed between the striking surface and the new bit of "tin". The hammer strikes the "tin" strip, and the bang is much better! If this doesn't work too well, the shrouding around the hammer, not the face of the hammer itself, can be taken back a fraction with a file, which is also worthwhile in terms of extra "Bang!" as the hammer squishes the cap better.
However, the things should really work properly from start. I blame the EU and "regulations".