"I'd give a .21 gunshot salute"
this should be "21 gun shot salute" not .21, as it is not referring to any caracteristic of the gun but rather to the honorary custom of firing 21 gun shots at the arrival or in this case, departure, of someone of great importance (typically in the military).
"I'd give a .21 gunshot salute" this should be "21 gun shot salute" not .21, as it is not referring to any caracteristic of the gun but rather to the honorary custom of firing 21 gun shots at the arrival or in this case, departure, of someone of great importance (typically in the military).