fired into Ladysmith a carrier shell without a fuze, which contained a Christmas pudding, two Union Flags and the message "compliments of the season". The shell is still kept in the museum at Ladysmith. Proof shot A proof shot is not used in combat but to confirm that a new gun barrel can withstand operational stresses. The proof shot is heavier than a normal shot or shell, and an oversize propelling charge is used, subjecting the barrel to greater than normal stress. The proof shot is inert (no explosive or functioning filling) and is often a solid unit, although water, sand or iron powder filled versions may be used for testing the gun mounting. Although the proof shot resembles a functioning shell (of whatever sort), so that it behaves as a real shell in the barrel, it is not aerodynamic as its job is over once it has left the muzzle of the gun. Consequently, it travels a much shorter distance and is usually stopped by an earth bank for safety measures. The gun, operated remotely for safety in case it fails, fires the proof shot, and is then inspected for damage. If the barrel passes the examination, "proof marks" are added to the barrel. The gun can be expected to handle normal ammunition, which subjects it to less stress than the proof shot, without being damaged. Guided shells Guided or "smart" ammunition features some method of guiding itself post-launch, usually through the addition of steering fins that alter its trajectory in an unpowered glide. Due to their much higher cost, they have yet to supplant unguided munitions in all applications. Unexploded shells The fuze of a shell has to keep the shell safe from accidental functioning during storage, due to (possibly) rough handling, fire, etc. It also has to survive the violent launch through the barrel, then reliably function at the appropriate moment. To do this it has a number of arming mechanisms which are successively enabled under the influence of the firing sequence. Sometimes, one or more of these arming mechanisms fail, resulting in a projectile that is unable to detonate. More worrying (and potentially far more hazardous) are fully armed shells on which the fuze fails to initiate the HE firing. This may be due to a shallow trajectory of fire, low-velocity firing or soft impact conditions. Whatever the reason for failure, such a shell is called