An apparatus for measuring a projectiles transverse displacement at {TAIL ~ muzzle exit} of {HEAD ~ a gun tube} which comprises: 
An apparatus for measuring a projectiles transverse displacement at { TAIL ~ muzzle exit } of { HEAD ~ a gun tube } which comprises :
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH