A .40 caibler Smith & Wesson cartridge is also called a 10mm. So it has a larger diameter bullet and more casing to hold more powder. Therefore it is a more powerful bullt than a 9mm Lugar Parabellum cartridge. The .40 S&W is 10mm in diameter, however, it is not normally referred to as 10mm, at least not in the U.S. The cartridge officially named 10mm was a different cartridge and cannot be fired from a .40 caliber handgun because it's too long to fit into the magazine or to feed into the barrel. The .40's case is 22 mm long and the 10mm is 25mm long. And whether a .40 caliber is more powerful than a 9mm is conjecture; it depends on whose statistics you choose to believe. In both calibers, as well as most any caliber, different cartridges have different specifications; different types of powder, different amounts of powder, lighter or heavier bullets, etc, all which can affect performance of the projectile, so to say that .40 is more power than 9mm is only correct when comparing some loads, but generally, .40 is considered more powerful that 9mm.
It depends to an extent on what you are trying to do.
7.62 mm (or 30 caliber) and 5.56 mm (or 223 caliber) are common rifle cartridges. Pistols, machine guns, and artillery will of course be different from these.
A 40mm handgun would fire a bullet the size of a golf ball. No such critter. There IS a .40 caliber handgun (about 10mm). There are dozens of larger caliber handguns than .40 caliber. They include the .41, .44. .45, .455. .460, .475, .500- and several others.
In April 1935, the armament was changed from two .303 caliber (7.7 mm) Vickers machine guns in each wing to four .303 caliber (7.7 mm) Brownings. in both cases the weapons were fully automatic.
No. 9mm and .40 are not interchangeable.
Possibly 40 mm. After the war, 40 mm then later 75 mm.
6.8mm / .270
http://www.industrial-enclosures.com/html/conversion-mm-inch.html
Short answer, a 9mm is smaller in diameter and lighter.
Roughly .275 or .28 caliber. Take MM divided by 25.4 (mm/inch) and you get caliber in hundredths of an inch.
40mm = 1.575 inches.Direct Conversion Formula40mm*1 in25.4 mm=1.57480315in
9 caliber is 0.09 inch, smaller than any standard ammunition made. 0.09 inch = 2.286 mm. Perhaps you were thinking "What caliber is 9 mm?". 9 mm = 0.354 inch = 35.4 caliber.