At around 9:30 of the movie, an order to fire the canons is given. The first canon fires before the fuse is lit.
The India General Service Medal (1854) was always issued with a clasp denoting the campaign. None of the ribbons seen in the film bear clasps. The Crimean War Medal was issued with and without clasps, so it is not inaccurate for Claybourne and Blaine to wear ribbons lacking clasps.