Anything 20mm or larger is considered a cannon - an entirely different class of weapons from small arms.
Anything 20mm and above is considered a cannon, which is an entirely separate category from small arms.
cannon
Smaller than 20mm.
ammunition box
About 100 of the early P-51A ( called NA 91 by North American ) were fitted with four 20mm cannon, many of these were sold to the RAF. In general it seems the 20mm guns were not as reliable as the 50 cal, and also the aircraft could only carry a limited supply of 20mm shells which were each about 3 times the weight of 50 cal.
I'm trying to find this too. A 2mm is small and a 20mm is large, but I have a 12mm brain cyst and cannot find how serious it may be and if it's causing my multitude of neurological symptoms.
It depends on what you classify as 'cannons' . Many aircraft were fitted with 20mm guns in exactly the same way as machine guns were. Some aircraft such as the Stuka, some other German aircraft and a few British aircraft were fitted with larger guns of 37- 40-mm calibre and these were often carried in pods under the wings and had very limited ammunition due to it's weight.
In guns including firearms, caliber or calibre is the approximate diameter of the barrel and by extension the projectile used in it, measured in inches or millimetres. The 20mm caliber ammo is the biggest one in production.
It was considered a scaled down - or miniature - version of the Vulcan 20mm cannon.
California has strict gun laws and I doubt that you can legally own a 20MM rifle in California. Usually the only guns available in California are small handguns.
mark a pt 20mm above xy planemark 20mm below
weight of ms hollow bar 20mm*20mm
The Paris gun of WWI. It weighed 256 tons. it was 28m long and fired a 240mm round. It was made by Krupp of Germany. The German army used it on Paris France.