Wonder Nine is a term coined by firearms author Robert Shimek which then became popular in America

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

n firearm

Firearm

A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...

-related magazine

Magazine

Magazines, periodicals, glossies or serials are publications, generally published on a regular schedule, containing a variety of articles. They are generally financed by advertising, by a purchase price, by pre-paid magazine subscriptions, or all three...

s during the 1980s. It refers to any handgun

Handgun

A handgun is a firearm designed to be held and operated by one hand. This characteristic differentiates handguns as a general class of firearms from long guns such as rifles and shotguns ....

 that is chambered in 9x19mm Parabellum and has a double stack magazine, as well as a double-action trigger for at least the first shot. Examples would be the Beretta 92

Beretta 92

The Beretta 92 is a series of semi-automatic pistols designed and manufactured by Beretta of Italy. The model 92 was designed in 1972 and production of many variants in different calibers continues today...

, Glock 17, CZ-75, and other such handguns. The simplicity of being able to fire the first shot just by pulling the trigger, a much-desired feature of double-action revolvers, combined with the high ammunition capacity (13-18 rounds, more than double what a revolver holds), are the "wonderful" features of a wonder-nine.

Even though such pistols were regarded as more efficient than revolver

Revolver

A revolver is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing. The first revolver ever made was built by Elisha Collier in 1818. The percussion cap revolver was invented by Samuel Colt in 1836. This weapon became known as the Colt Paterson...

s, most American police departments were still using revolver

Revolver

A revolver is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing. The first revolver ever made was built by Elisha Collier in 1818. The percussion cap revolver was invented by Samuel Colt in 1836. This weapon became known as the Colt Paterson...

s, chambered in calibers such as .38 special

.38 Special

The .38 Smith & Wesson Special is a rimmed, centerfire cartridge designed by Smith & Wesson. It is most commonly used in revolvers, although some semi-automatic pistols and carbines also use this round...

 and .357 Magnum

.357 Magnum

The .357 S&W Magnum , or simply .357 Magnum, is a revolver cartridge created by Elmer Keith, Phillip B. Sharpe, Colonel D. B. Wesson of firearms manufacturer Smith & Wesson, and Winchester. It is based upon Smith & Wesson's earlier .38 Special cartridge. The .357 Magnum cartridge was introduced in...

, and would not follow the Wonder Nine trend until the early 1990s with the subsequent adoption of 9mm and .40 S&W

.40 S&W

The .40 S&W is a rimless pistol cartridge developed jointly by major American firearms manufacturers Winchester and Smith & Wesson. The .40 S&W was developed from the ground up as a law enforcement cartridge designed to duplicate performance of the FBI's reduced velocity 10mm cartridge which could...

pistols.