Editing Shell (projectile) (section)

===Fixed ammunition===
Fixed ammunition has three main components: the [[fuze]]d projectile, the [[Cartridge (firearms)|casing]] to hold the propellants and [[Detonator|primer]], and the single propellant charge. Everything is included in a ready-to-use package and in British ordnance terms is called [[Glossary of British ordnance terms#Fixed QF|fixed quick firing]].  Often guns which use fixed ammunition use [[Rifled breech loader#The sliding block|sliding-block]] or sliding-wedge breeches and the case provides [[obturation]] which seals the [[Breech-loading weapon|breech]] of the gun and prevents propellant gasses from escaping.  Sliding block breeches can be horizontal or vertical.  Advantages of fixed ammunition are simplicity, safety, moisture resistance and speed of loading.  Disadvantages are eventually a fixed round becomes too long or too heavy to load by a gun crew.  Another issue is the inability to vary propellant charges to achieve different velocities and ranges.  Lastly, there is the issue of resource usage since a fixed round uses a case, which can be an issue in a prolonged war if there are metal shortages.<ref name=":Hogg">{{Cite book|title=Artillery|last1=Hogg|first1=Ian |last2=Batchelor |first2=John H. |date=1972|publisher=Scribner |isbn=0684130920|location=New York|oclc=571972}}</ref>