A question RE: Late War automatic AA weapons

[NickM]

I am curious as to what types of Automatic AA weapons the Western Allies used in Western Europe-particularly from 1944 onwards; I am familiar with the American 'quad Fifty' & the Bofors 40mm, used by nearly everyone in the AEF; However, I was wondering if there were other AA weapons used by the US, Britain & her Commonwealth Allies. I've read lots of accounts of LW combat & on numerous occasions I've run across pilots mentioning being shot down or damaged by 20mm AA guns. Now, other the the pintle mounted Orlikon 20mm used by the USN/RN I am not familiar with a 'land based' 20mm AA system used by the Allies...so it appears that there is a gap, not only between .50 caliber & 40mm but also in my working knowledge of these weapons systems.
So...am I missing something?

thank you, ahead of time;

NickM