Lindell's assessment noting that the entry level for medium-sized calibres "is now being sort of reset." While it was once the case that 20mm would be the 'entry-level' calibre in the medium calibre domain, 25mm would be good, and 30mm would be best, "now we're finding that really 30mm is insufficient and you've got to really go towards the 40mm and 50mm (calibres)." For this reason, he said that his company's CTA-40 weapon aimed to pack the power of a 50mm weapon, within the volume of a 30mm: "50mm calibre', medium calibre on these turrets, is just huge ...
Much of the debate over calibres for IFVs naturally comes down to cost.
Yet the increasing complexity of the battlefield has impacts across the ranges of calibres. On the large calibre side, the requirements have shifted from "kind of anti-armour-centric rounds to more multi| purpose effects," said Lieutenant Colonel Kyle McFarland, product manager for large calibre ammunition at the US Army's I Ammunition Programme Executive Office (PEO), which covers munitions ranging from 105mm to 120mm.
A survey of guns and calibres would be almost endless, but writing space is limited.
There are three calibres and four guns to consider.
First, the calibres. The 9-mm would not even have been considered as a fighting calibre on this side of the ocean had not a huge load of French ammunition landed on English shores in June 1940.