Doubtful. There is no smell of either gunpowder nor guncotton.
[Sebastian would much prefer to free Ciel before thinking of himself, but once it's established no amount of dexterity will unlock the contraption he abandons Ciel's leg to instead tug at his own manacle, as hard has he possibly can - there is, after all, no risk of Sebastian snapping his own leg in two.
Of course, nothing happens, and Sebastian frowns. Weak. That was pitifully weak, for an attempt at 'as hard as he possibly can'.]
I believe its function is, rather, to subdue. Normally it would be child's play for me to break something like this.
[And surely, even if Sebastian's mentally unwell that shouldn't affect his physical strength?]