I am not aware that the British manufactured "tropical ammunition."Yoozername wrote: Muzzle velocity seems to be affected by temps more so than any other parameter. Anyone know if the Brits did likewise? That is, make tropical ammunition???
The ambient temperature does have an effect on MV as warmed propellant generates a bit more oomph. It is one reason why ammunition should be stored in a shelter and not left lying in the sun.
Firing characteristics also change as the gun barrel and breech warm after repeated firing. There is something called the "Cold gun effect" with the first round being outside the norm.
High rates of fire can heat the gun far hotter than even a tropical sun. So hot that the round can eventually "cook off." This happened to at least one battery in 51st Highland Division that were left loaded at the end of the fireplan for Op BAYTOWN, the invasion of Italy across the straits of Messina. It was night. The assault troops were ashore and the sea was full of boats. The guns were allowed to burst.